Railroads and the Deadlocked Transportation Act

Just before the House and Senate left for an August recess, they managed to pass a three month patch so that the government could continue to fund mass transit and highway projects. Funding highway projects used to be very popular and bipartisan. Lots of people were employed laying Rebar and pouring concrete and at one time the Transportation bill was very popular.

The current systems was set up under President Eisenhower in 1956. He supported a nationwide highway system that would allow the rapid movement of defense forces around the continental United States. The result was the Federal-Aid Highway Act of 1956 also known as the National Interstate and Defense Highways Act. Below is the key procedural vote in the Senate (having to do with labor issues). The Senate then went on to pass the bill by voice vote.

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The 1956 Act set up the Highway Trust Fund that received money from a federal fuel tax. These funds were intended for the construction of highways. The original gas tax was $0.03 per gallon and that increased in increments over the years to $0.184 per gallon. A separate trust fund was established to fund mass transit projects.

The problem that Congress is now stuck with is the fact that cars and trucks are now more fuel efficient so that less money is flowing into the Trust Fund at the same time as the interstate system, roads, and bridges are deteriorating. Congress, especially Republicans, is loath to increase gasoline taxes. Instead they have used various budget gimmicks to transfer general revenue into the fund which only prolongs the crisis.

If this were not bad enough, the Senate bill combines the Transportation bill with the renewal of the Export-Import bank which many Republicans oppose as crony capitalism. Given these conflicting objectives it is no surprise that the 65-34 vote in the Senate shown below has no ideological structure whatsoever. Both parties are split internally over the bill which will make things all the more difficult to reach some sort of deal with the House in September.

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But inside this bill is a Time Bomb that if it goes off could quite literally shut down the US economy. That Time Bomb is Positive Train Control (PTC) which is supposed to be in place on the railroads nationwide by the end of 2015. In effect PTC would be a “fail-safe” system that would prevent accidents such as the 12 September 2008 collision of a Metrolink (Los Angeles system) commuter train with a Union Pacific freight train head-on while the Metrolink engineer was busy texting. Twenty-five people were killed and it caused Congress to pass a bill in October 2008 mandating PTC on the entire nationwide railroad system.

Congress appropriated no funds for the railroads to build this system even though the major freight railroads — BNSF, UP, CSX, NS — run no passenger trains and serious wrecks of freight trains are relatively rare. PTC requires a complex system of computers and wireless radio control so that engines can be remotely controlled. None of the major freight railroads have finished building this system (for example, Congress did not order the FCC to release spectrum on an emergency basis to the railroads!).

In the Transportation Act passed by the Senate there is a three year delay until 31 December 2018 to give time for the major railroads to implement PTC. A number of members of Congress such as Chuck Schumer (D-NY) oppose any delay regardless of the consequences. Unless the delay is passed, in January the freight railroads will have to decide to stop hauling toxic inhalation materials and close their tracks to commuter trains. This drastic step would put them in compliance with PTC but would violate the basic law that the Railroads are common carriers (see Trains magazine, October 2015, page 6 for a discussion). This would set off a major national crisis. Like it or not hazardous materials such as Chlorine and Sulfuric Acid have to transported by rail. They have to move or major industries will grind to a halt. Ditto the commuter rail. If commuter trains are stopped from using the freight rail lines massive traffic jams will be the result.

This whole sorry spectacle is yet another sign of how dysfunctional Congress has become.

Senate Medians 1789 – 2014

Jeff Lewis and Keith Poole, 24 August 2015

Below we show the Senate Chamber and Party Medians on the first DW-NOMINATE dimension for the first 113 Congresses with 95 percent credible intervals based upon 250 parametric bootstrap trials. (The Working Paper was later published in Political Analysis, 17(3):261-275, 2009).

The graph below shows the Senate Median from 1789 to 2014 (Senates 1 – 113). During the three stable two-party periods in American history the Senate Median will be in the majority party. For example, in the very early period when the Federalists dominated the Jeffersonians, the Senate Median was to the right. The changes in the Senate Median over time follow the historical analysis of Poole and Rosenthal in Congress: A Political-Economic History of Roll Call Voting, chapters 4 and 5.

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The graph below shows the Party Medians and 95 percent credible intervals for the Federalist-Jeffersonian Republican Party System (1789 – 1811). The movement to the right by the Federalists should not be over interpreted since they only had seven seats in the 11th (1811-12) Senate. The opposition of the Federalists to the War of 1812 resulted in the collapse of the Party during The Era of Good Feelings.

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The graph below shows the Party Medians and 95 percent credible intervals for the Whig-Democrat Party System (1827 – 1848). The Democrats were the dominate party through this period but the second dimension split the two parties along North vs. South lines. The conflict over Slavery and its extension to the territories caused the collapse of the Whig Party after the Compromise of 1850 and despite the efforts of Senator Stephen Douglas (D-IL) the admission of more states during the 1850s did not settle the North-South divide within the Democratic Party.

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Finally, the graph below shows the Party Medians and 95 percent credible intervals for the Republican-Democrat Post-Reconstruction Party System (1879 – 2014). The trend to greater polarization in the modern era is clearly evident at the end of the series.

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Alpha-NOMINATE Applied to the 114th House

Following up on our previous post, below we apply Alpha-NOMINATE to the 114th House. There have been 489 total votes in the House as of the August recess of which 435 are scalable (at least 2.5% in the minority). We used the R version of Alpha-NOMINATE to perform the analysis. We used 2000 samples from a slice sampler in one dimension with a burn-in of 1000. The first graph shows the Trace and Density plots for alpha.


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The mean was 0.99965 with a standard deviation of 0.0003347 strongly indicating that the Representatives’ utility functions were Gaussian.

The next four plots show the estimated ideal points for the 434 scalable Representatives along with their 95% Credible Intervals. On the left, Representative Grijalva (D-AZ) is located at -2.266. His 95% credible interval runs from -2.751 to -1.87. The five Republicans on the right end are Huelskamp (R-KS) at 2.62 (1.79 – 3.34), Sanford (R-SC) at 4.35 (4.06 – 4.61), Massie (R-KY) at 4.43 (4.20 – 4.66), Amash (R-MI) at 4.48 (4.27 – 4.70), and Jones (R-NC) at 5.27 (5.06 – 5.50).
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The Median of the Democratic Party is -1.310 with a standard deviation of 0.0284 and the Median of the Republican Party is 0.9490 with a standard deviation of 0.0224. The probabilities for the median Representative are 0.068 for Thompson (R-PA), 0.065 for Upton (R-MI), 0.060 for Young (R-AK), 0.059 for Reed (R-NY), 0.058 for Valadao (R-CA), and 0.057 for Turner (R-OH). Assuming that the Republicans vote as a bloc (highly unlikely!), the probabilities for the Filibuster Pivot are 0.049 for Rice (D-NY), 0.042 for Keating (D-MA), 0.039 for Connolly (D-VA), and 0.038 for Gabbard (D-HI), Carney (D-DE), and Delbene (D-WA). Again, President Obama will likely have the votes to prevent a veto override of his nuclear deal with Iran.

Alpha-NOMINATE Applied to the 114th Senate

Updated: 17 August 2015

Alpha-NOMINATE is a new form of NOMINATE that is fully Bayesian and is meant to replace W-NOMINATE which is now about 32 years old (the multidimensional version, written by Nolan McCarty and Keith Poole is 24 years old). NOMINATE was designed by Keith Poole and Howard Rosenthal during 1982-1983. It used a random utility model with a Gaussian deterministic utility function (see pages 14 – 15 of the linked 1983 paper) and logistic error (random draws from the log of the inverse exponential). The Gaussian deterministic utility function is able to capture non-voting due to indifference and alienation.

Alpha-NOMINATE is a mixture model in which legislators’ utility functions are allowed to be a mixture of the two most commonly assumed utility functions: the quadratic function and the Gaussian function assumed by NOMINATE. The “Alpha” is a parameter estimated by Alpha-NOMINATE that varies from 0 (Quadratic Utility) to 1 (Gaussian Utility). Hence, in one dimension with Alpha = 0, Alpha-NOMINATE is identical to the popular IRT model. Thus Alpha-NOMINATE can actually test whether or not legislators’ utility functions are Quadratic or Gaussian.

Below we apply Alpha-NOMINATE to the 114th Senate. There have been 262 total votes in the Senate as of the August recess of which 220 are scalable (at least 2.5% in the minority; that is, votes that are 97-3 to 50-50). We used the R version of Alpha-NOMINATE to perform the analysis. We used 2000 samples from a slice sampler in one dimension with a burn-in of 1000. The first graph shows the Trace and Density plots for alpha.


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The mean was 0.9916 strongly indicating that the Senators’ utility functions were Gaussian.

The next plot shows the estimated ideal points for the 100 Senators along with their 95% Credible Intervals. On the left, Senator Sanders (I-VT) is located at -2.74 just off the left edge of the plot. His credible interval runs from about -3.31 to -1.89. Off the right end and not visible are Senator Cruz (R-TX) at 3.84 with a credible interval that runs all the way from 0.958 to 5.398 and Senator Paul (R-KY) at 5.175 with a credible interval that ranges from 4.766 to 5.750.
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The median of the Republican Party is 0.7562 with a standard deviation of 0.0331 and the median of the Democratic Party is -0.9318 with a standard deviation of 0.0583. The probabilities for the median Senator are 0.575 for Murkowski (R-AK), 0.158 for Graham (R-SC), and 0.128 for Heller (R-NV). Assuming that the Republicans vote as a bloc, the probabilities for the the Filibuster Pivot are 0.251 for King (I-ME), 0.218 for Tester (D-MT), 0.197 for Bennet (D-CO), and 0.154 for Warner (D-VA). Again, assuming that the Republicans vote as a bloc, the probabilities for the Veto Override Pivot are 0.174 for Nelson (D-FL), 0.130 for Coons (D-DE), 0.125 for Feinstein (D-CA), and 0.115 for Shaheen (D-NH). President Obama will likely have the votes to prevent a veto override of his nuclear deal with Iran.

An Update on the Presidential Square Wave (July 2015)

Below we plot the first dimension DW-NOMINATE Common Space scores—which are now updated weekly—of the presidents in the post-war period, which we refer to as the “presidential square wave” due to its shape. An ideological score is estimated for each president throughout the entirety of their tenure in office by scaling their “votes” on a subset of roll call on which they announce a position (measured using CQ Presidential Support Votes). Negative DW-NOMINATE scores indicate greater liberalism and positive scores indicate greater conservatism. The presidential scores are directly comparable across time and with members of Congress.

These presidential DW-NOMINATE scores are estimated using all available CQ presidential support roll calls through 2013. CQ does not issue all of its presidential support roll calls until the print version of its congressional roll call guide comes out, and so only a fraction of the 2015 votes are available.

President Obama fits the spatial model estimated by DW-NOMINATE extremely well, with over 95% of his “votes” correctly classified. Obama has moved slightly back towards the center (-0.343) from the last presidential square wave. He is now the second most moderate Democratic president of the post-war era, coming in just to the left of LBJ (-0.337). President Eisenhower is the most moderate president (0.293) of the post-war era.

Our results differ from those of organizations like InsideGov and OnTheIssues, which code presidential issue statements on liberal-conservative scales and place Obama much further left. We suspect that our method, which uses declared presidential positions on roll calls before Congress to place both sets of actors in the same ideological space, accounts for widespread (though not universal) Republican support on votes concerning judicial appointments, national security, and trade.

Among members of the 114th Congress, President Obama is ideologically closest to Representatives David Price (D-NC) [-0.34], Ted Lieu (D-CA) [-0.339], Bill Keating (D-MA) [-0.345], and Adam Schiff (D-CA) [-0.345] in the House; and Senators Patty Murray (D-WA) [-0.344], Ben Cardin (D-MD) [-0.333], and Chuck Schumer (D-NY) [-0.353] in the Senate.

Note: K7moa.com and the Voteview Blog were hacked and destroyed in early March, which resulted in the loss of most of the old blog posts. We will be continually restoring and updating some of the old posts. Please send an email if there is a specific post that you would like to see restored. Thanks.

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Ideological Locations of the 2016 Presidential Contenders

Below we plot the ideological positions of the 2016 presidential contenders who have served in Congress at some point in their political careers. We use weekly Common Space DW-NOMINATE scores, which are compiled based on the entirety of legislators’ roll call voting records and comparable between House and Senate, as our measures of ideological position. The distribution of scores for House and Senate Democrats and Republicans in the current (114th) Congress are also shown with smoothed histograms.

Senator Bernie Sanders (I-VT) is certainly in the left-wing of the Democratic Party and to the left of former Senator Hillary Clinton (D-NY), but is not the most liberal member of the 114th Senate. That distinction belongs to Senator Elizabeth Warren (D-MA) (though the most liberal member of the entire 114th Congress is Rep. Barbara Lee [D-CA]). Former Senator Jim Webb (D-VA) is well to the right of Sanders and Clinton, and would be among the most moderate Democrats in the current Congress were he still serving.

Among the Republican contenders, Senators Ted Cruz (R-TX) and Rand Paul (R-KY) have nearly identical ideological scores that place them on the most rightward edge of their party. Senator Marco Rubio (R-FL) is among the more conservative members of his party, but noticeably to the left of Cruz and Paul. Former Reps. Bobby Jindal (R-LA) and John Kasich (R-OH) have ideological scores that place them on the moderate side of their party (at least in the 114th Congress).

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Passage of the Pacific Rim Trade Pact

Congress handed President Obama a major victory on the Pacific Rim Trade Pact this week. The Senate had combined Fast Track Authority and the displaced workers assistance into one bill. As we show in our previous post Fast Track Authority passed the House 219 Yea – 211 Nay but the displaced workers assistance was defeated 128 Yea – 300 Nay. The House then brought up a stand-alone bill granting the President Fast Track Authority last week and it passed. We use our Weekly Constant-Space DW-NOMINATE Scores to do the vote plots. The House vote to approve FTA is shown below:

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The vote was 218 Yea – 208 Nay (the missing “Yea” in the plot is Speaker Boehner who has not voted enough time to be scaled). The Republicans split 190 Yea to 50 Nay and the Democrats split 28 Yea to 158 Nay.

The Senate took up the Fast Track Authority bill on Thursday, 24 June 2015, and passed it 60 Yea to 38 Nay after a cloture motion passed on Wednesday, 23 June 2015, 60 Yea to 37 Nay. The final passage of FTA in the Senate is shown below:

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The five Republicans who voted Nay were Collins (R-ME), Cruz (R-TX), Paul (R-KY), Sessions (R-AL), and Shelby (R-AL). Collins, Paul, Sessions, and Shelby all voted Nay on 22 May 2015 against the combination of FTA and the displaced workers assistance bill. Cruz had voted Yea but switched his vote Nay this time. Lee (R-UT) voted against the combined bill on 22 May but did not vote on the stand-alone FTA. FTA was then sent to President Obama.

With the Fast Track Authority having cleared both chambers it was relatively easy to pass the displaced workers assistance. It passed in the Senate on Wednesday 24 June 2015 by a vote of 76 Yea to 22 Nay. This vote is shown below:

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In the House the displaced workers assistance bill passed by a wide majority 286 Yea to 128 Nay. This time The Democrats voted for the bill 175 Yea to only 6 Nay in contrast to the vote on 12 June 2015 where they voted against the assistance portion of the combined bill 40 Yea to 144 Nay despite an appeal from President Obama for their support. The final passage vote is shown below:

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The six Democrats who voted Nay were Boyle (D-PA), Cartwright (D-PA), Grijalva (D-AZ), Lynch (D-MA), and Thompson (D-MS).

President Obama’s major victory was made possible by Republican leaders in Congress standing with him and using deft legislative maneuvers to get the FTA and assistance packages through Congress. President Obama may be in his last 18 months as President but he is far from a lame duck.

Voting on the Pacific Rim Trade Pact

President Obama’s effort to secure “Fast Track” authority to finish the negotiations on the Pacific Rim Trade Pact appears to be in serious jeopardy after the displaced Workers Aid portion of the bill was defeated by a vote of 126-302. The Senate passed a bill on May 22nd that coupled fast track with the displaced workers aid. We use our Weekly Constant-Space DW-NOMINATE Scores to do the vote plots. The Senate vote is shown below:

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Five Republicans voted against the bill — Collins (ME), Lee (UT), Paul (KY), Sessions (AL), and Shelby (AL). The blue “R” furthest to the right is actually Lee and Paul because they have essentially identical coordinates — (0.925, -0.159) and (0.927, -0.156), respectively. The blue “R” furthest to the left is Collins. Getting the 62 votes to pass the trade bill was a heavy lift for McConnell and President Obama. Any changes in the bill in the House would likely mean its defeat in the Senate.

The bill unraveled in the House where there were separate votes on the displaced workers aid portion and the fast track portion. The displaced workers aid went down by a lopsided 126-302 vote:

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(The two missing “Nay” votes are Speaker Boehner (who has not voted enough times for coordinates to be estimated) and Trent Kelly (R-MS) who was just elected to replace Alan Nunnelee (R-MS) who died of brain cancer in February.) The cutting line actually produces more errors — 136 — than “Yea” votes — 126. In CS DW-NOMINATE we only constrain roll call midpoints to be within the unit circle in two dimensions (technically, an ellipse because we use a weighted Euclidean metric).

Neither Political Party was happy with the bill and this is reflected in the lopsided defeat of the workers aid portion. Many Democrats believe that the Trade Deals of the past 25 years have worsened income inequality as jobs moved overseas. How much free trade has contributed to income inequality is not clear but there is no denying the steep increase in inequality since 1970:

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As Emmanuel Saez shows the rich have done well since the Clinton years. Here is his Table 1:

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After the defeat of the displace workers aid package the House then voted on the Fast track portion of the bill. This passed by a vote of 219 – 211:

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(The two missing “Yea” votes are Speaker Boehner and Trent Kelly.) Although the PRE is a respectable 0.62 ((211-81)/211) there was substantial opposition within each Party to the respective majority positions.

Speaker Boehner and President Obama are now faced with the prospect of finding the votes to get the displaced workers aid passed on Tuesday or the whole trade bill will be dead.

More on Asymmetric Polarization: Yes, the Republicans did it!

In our last post we showed the Party Means for the House and Senate since 1879. We used our Weekly Constant-Space DW-NOMINATE Scores to do those graphs. Below is the graph for the House which shows the Republican Party moving rapidly to the Right after the late 1960s. In contrast, the movement of the Democratic Party to the Left is entirely due to the Southern Democrats becoming indistinguishable from the Northern Democrats. Indeed, the Northern Democrats have not moved since the 1960s.

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Not everyone believes the above graph. For example, Peter Wehner argued in a NYT op-ed that the “Democratic Party … has moved steadily to the left since the Clinton presidency.”

The purpose of this Blog is not to engage in debate with pundits. We use it to show the results of our 33 year research project on the history of Congressional Voting (note the discussion on page 14 of this 1983 Working Paper). Consequently, the purpose of this post is to show that Asymmetric Polarization is real and is not some methodological artifact of our DW-NOMINATE method.

Our first experiment is to run DW-NOMINATE just on the House for Congresses 1-113 using random starting coordinates to see if the asymmetric polarization observed in the modern era holds up. In particular, if a member’s coordinate on either dimension was negative we drew a uniform random number between -1 and 0 and inserted into the starting coordinates. Similarly, if the member’s coordinate on either dimension was positive we drew a uniform random number between 0 and +1. We then estimated the cutting lines for the roll calls using the Cutting Line Procedure in Optimal Classification. We used the Poole and Rosenthal Constant Model where each member’s ideal point is the same throughout his/her career in Congress. For the first five iterations we fixed the second dimension weight to 0.4 and Beta to 7.5. Iterations six through fifteen reverted to the normal DW-NOMINATE algorithm. Below is graph of the Party means of Houses 46 to 113 (1879 – 2014). Note that it shows almost exactly the same pattern as the figure above.

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Our second experiment is to run Optimal Classification on the House and Senate for Congresses 1 – 113 simultaneously using the 650 members who served in both the House and Senate as “glue” (bridge observations). Below is a graph of the Party means of Houses 46 to 113 (1879 – 2014). It is virtually identical to the CS DW-NOMINATE House graph shown above.

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Our final experiment is to run the Basic Space procedure (Poole, 1998) on W-NOMINATE scores for every House and Senate for the 75th to the 113th Congresses (1937 – 2014). This application is the same as that shown in Poole (1998, p.982-989). The graph of the Party Means of Houses 75 to 113 is shown below.

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The same pattern occurs in the Basic Space application to the W-NOMINATE scores but it is obviously not as “clean” as the other graphs. Nevertheless, the pattern is the same. The Republicans move to the Right while the two wings of the Democratic Party converge. The Basic Space result is very strong evidence because each W-NOMINATE configuration is scaled separately and the first dimension is constrained to range from -1.0 to +1.0. Hence, the only way that the Republican mean could be moving to the Right is through replacement of moderates by conservatives.

Below we reproduce a post we did on our old Blog in 2012. Voteview.com was hacked by Chinese hackers and completely destroyed in early March. All the old Blog posts were lost and we moved the Blog to wordpress for security reasons.

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Polarization is Real (and Asymmetric)
by Nolan McCarty on May 15, 2012 · 14 comments
in Legislative Politics

This post is co-authored with Keith Poole, Howard Rosenthal, and Chris Hare. It is cross-posted at voteview blog.

The recent outburst of scholarly and popular interest in political polarization has attracted attention to the methods we use to measure this phenomenon. One frequently voiced concern (see a recent column by Sean Trende) is that Congress may not have polarized as we have claimed in publications and blogs stretching as far back as 1984. The concern is that the meaning of ideological (NOMINATE) scores are tied to the legislative and historical context of the roll call votes that are used to estimate them. For example, the content of roll calls votes cast by members of 90th Senate that dealt with the Vietnam War, civil rights, and funding for LBJ’s “Great Society” programs are quite different than those votes cast in the current Senate. Thus, being the most conservative Senator (with a score of 1.0) in 1968 would mean something different than having an identical 1.0 score in 2012.

Indeed, temporal comparisons should not be made for ideal points generated from static scaling methods. Static methods (like W-NOMINATE) treat each legislative session separately and there is no valid way to compare the scores of legislators from different years. However, we developed a dynamic methodology, DW-NOMINATE (McCarty, Poole and Rosenthal 1997), to allow for over-time comparisons of legislator ideological positions. The key innovation is the use of “bridge” legislators—members of Congress (MCs) who have served in multiple sessions—to compare the positions of legislators who have never served together.

A sports analogy to the overlapping cohorts method is the “common opponents” statistic. If we want to compare two teams who have not played each other, we compare their performances against a common opponent(s). Likewise, MCs who have not served together can be compared with the use of a “bridge” legislator who has served with both. For example, if we know that Sen. George McGovern (D-SD) is more liberal than Sen. Patrick Leahy (D-VT), and that Sen. Leahy is more liberal than Sen. Max Baucus (D-MT), then we can say that Sen. McGovern is more liberal than Sen. Baucus. Though intransitivities may arise cases involving 3 or more sports teams, Poole shows in his 2007 Public Choice article “Changing Minds? Not in Congress!” that MCs remain remarkably static in their ideological positions over the course of their careers. Thus, we are on much firmer ground in making over-time comparisons between MCs with the caveat that we cannot compare members outside of one of the stable, two-party periods of American history. For that reason, when we discuss current polarization we focus on the period from the end of Reconstruction in 1877 to the current period.

With the use of overlapping cohorts, we can make the over-time comparisons needed to analyze polarization. A good example is Senator Richard Lugar (R-IN), who, after his primary defeat last week, will have served in the Senate between 1977 and 2013. As David Karol points out, Lugar himself did not change very much over time: he was a reliable conservative who moved only somewhat towards the center during a 30-plus year career (from a DW-NOMINATE first dimension score of 0.348 to 0.241). DW-NOMINATE scores range (with slight simplification) from minus 1 to 1 or a band of two units. So in 30 years, Senator Lugar moved just five percent on the liberal-conservative dimension.[1]

For Lugar, what is more dramatic is the change in his ideological position relative to the Senate Republican Caucus. In his first term in Congress, Senator Lugar was the 23rd most moderate Republican in the Senate; in the most recent term (through 2011), he was the fifth most moderate. Even if he had maintained his freshman score of 0.341, he would still have been the 12th most moderate Republican in the 112th Congress. This repositioning occurred because almost every new cohort of Republican Senators has been more conservative than Senator Lugar. That fact is the basis for our claim that the Republican Party has moved to the right.

To be sure, political polarization is not entirely asymmetric. Congressional Democrats have moved slightly to the left during this period, but most of this is a product of the disappearance of conservative Southern “Blue Dog” Democrats. But the northern Democrats of the 1970s are ideologically indistinguishable from their present-day counterparts, with average scores around -0.4.

Though Democrats have not moved nearly as much to the left as the Republicans have to the right, they have also contributed to polarization, in our opinion, by embracing identity politics as a strategic tool. In Roosevelt’s New Deal, the Democrats advocated redistribution and regulation of business. These issues remain active to some extent, but with time emphasis has shifted to issues centered on race, gender, ethnicity, or sexual preference (Gerring 1998). This distinction, however, is not necessarily picked up in roll call voting. But it does represent an important rhetorical shift from the Roosevelt and Truman-era Democratic Party that likely worsens political and social divides.

Nonetheless, we should be careful not to equate the two parties’ roles in contemporary political polarization: the data are clear that this is a Republican-led phenomenon where very conservative Republicans have replaced moderate Republicans and Southern Democrats. Thomas Mann and Norm Ornstein do an excellent job of navigating these trends in their new book: It’s Even Worse Than It Looks: How the American Constitutional System Collided With the New Politics of Extremism.

Moreover, the rise of the “Tea Party” will likely only move Congressional Republicans further away from the political center. For example, the five Tea Party-backed Senators elected in 2010 (Senators Rubio, Paul, Toomey, Lee, and Johnson) have an average first dimension DW-NOMINATE score of 0.795. Moderate MCs (especially Republicans) are increasingly likely to be “primaried” out (e.g., Sens. Bob Bennett (R-UT), Joe Lieberman (D-CT), and Lisa Murkowski (R-AK), as detailed in a recent post on k7moa.com [The post was lost in the break-in and destruction of k7moa.com]).

The public policy consequences of polarization are immense. Bipartisan agreements to address looming issues like the budget deficits, spending on entitlement programs, and immigration are now almost impossible to reach. In contrast, during Ronald Reagan’s administration, about 40% of the members of Congress could be described as moderates. Reagan was thus able to forge major bipartisan agreements to cut taxes in 1981, raise taxes in 1982, fix Social Security (the Greenspan Commission) in 1983, and pass immigration reform (which included amnesty) and major tax simplification in 1986.

As shown in the second pair of figures below [see Figures above], only about 6% of Representatives and 13% of Senators in the 112th Congress can be described as moderates (defined as having a first dimension DW-NOMINATE score between minus 0.25 and plus 0.25). This absence forces major legislation, such as President Obama’s health care package, to be passed by one party. But unlike major bipartisan efforts (e.g., the Social Security Act of 1935, the Civil Rights Act of 1964, or welfare reform in 1995), legislation passed by one party is less likely to earn popular acceptance (as evidenced by the partisan breakdown in opinion on “Obamacare”).

Polarization is real. Arlen Specter was reelected to the Senate as a moderate Republican in 2004. In the 2010 election, he was replaced by Pat Toomey. Do academics and pundits really want to argue that Republicans have not moved to the right and that Pat Toomey might be more moderate than Arlen Specter because the congressional agenda has changed? Let’s not get picky about polarization. It’s for real, and it is making the United States dysfunctional.

1 Legislators’ DW-NOMINATE scores are allowed to move as a linear function of time, while a single coordinate is estimated for each legislator with the Common Space procedure; methodological issues aside, the linear and constant methods produce yield the same pattern of contemporary political polarization.

References:
Gerring, John. 1998. Party Ideologies in America, 1828-1996. Cambridge: Cambridge University Press.

McCarty, Nolan M., Keith T. Poole, and Howard Rosenthal. 1997. Income Redistribution and the Realignment of American Politics. AEI Studies on Understanding Economic Inequality. Washington, DC: AEI Press.

House and Senate Party Means 1879 – 2015

Below we use Weekly Common Space DW-NOMINATE scores to plot the means of the House and Senate Democrats and Republicans 1879 – 2015 (May 31).  The Democrats in the House for the first time since 1921 are homogeneous across the North and South (the 11 States of the Confederacy plus Kentucky and Oklahoma).  The Republicans in the 114th House have almost exactly the same mean as they had in the 113th House so we may, at last, see a leveling off of polarization.  Indeed, the slight increase in polarization in the House from the 113th to the 114th (see below) is due to a slight shift to the left of the Democratic Party mean due to the Southern Democrats shifting left.
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In the Senate the Southern Democrats are more moderate than the Northern Democrats but both groups have shifted to the left.  The Republicans have shifted to the right.  This is why the uptick in polarization in the Senate is larger than the House (see below).

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The results indicate that polarization (i.e., the distance between the two parties on the first dimension [Liberal vs. Conservative]) has increased slightly in both the House and Senate.  In an earlier post we thought that the polarization in the Senate had dropped a little.  That was an error.  We used the wrong dataset.  The figure below is correct and uses all the roll calls through 31 May 2015.

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I bears repeating that the trend to polarization has been largely due to the Republican Party moving to the right since the 1976 elections. In contrast, the Northern Democrats in both Chambers have barely budged in the past 40 years. What has happened is the the Democratic party has become much more homogeneous.