An Update on the Presidential Square Wave

Below we plot the first dimension DW-NOMINATE Common Space scores 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 2014 votes are available.

Very little has changed from the last presidential square wave. President Obama fits the spatial model estimated by DW-NOMINATE extremely well, with over 95% of his “votes” correctly classified. Obama has moved very slightly leftward (-0.367) and is now just to the left of LBJ (-0.346) and right of Truman (-0.368), though this trio is virtually ideologically indistinguishable. President Eisenhower is the most moderate president (0.293) of the post-war era.

Among members of the 113th Congress, President Obama is very ideologically close to Representatives Stephen Lynch (D-MA) [-0.364] and Loretta Sanchez (D-CA) [-0.369] in the House, and Senators Patty Murray (D-WA) [-0.367] and Mark Udall (D-CO) [-0.359] in the Senate.

Click image to enlarge

House and Senate Polarization 1879 – 2014

Below we show the polarization of the Political Parties for the 1879 through 2014 period (46th to 113th Congresses). Polarization is measured by the distance between the means of the Democrat and Republican Parties on the first (Liberal vs. Conservative) DW-NOMINATE dimension. Polarization is now at a Post-Reconstruction high in both the House and Senate.

Click image to enlarge

Below are the Party means for the House on the first DW-NOMINATE dimension. For the Democrats we show the means for the Northern and Southern wings of the Party (We use the CQ definition of South; the 11 States of the Confederacy plus Kentucky and Oklahoma). In the past three Congresses the difference between the Northern and Southern Democrats has disappeared.

Click image to enlarge

Below are the corresponding Party means for the Senate on the first DW-NOMINATE dimension. The pattern is essentially the same as the House. However, the Southern Democratic Senators as a group tend to be more moderate than their Northern counterparts.

Click image to enlarge

Below are the Party mean graphs for the House and second for the second DW-NOMINATE dimension. This dimension usually picks up regional differences between the two major parties. Before the Civil War the second dimension picked up the North vs. South division on Slavery. In the Post Reconstruction period the second dimension picked up regional differences on soft vs. hard Money (bimetalism, gold and silver) and beginning in the late 1930s Civil Rights. In the past 20 years the second dimension has faded in importance and issues that used to divide the parties internally — e.g., gun control, abortion — now load almost entirely on the first dimension. This is explored in detail in Keith T. Poole and Howard Rosenthal (2007) Ideology and Congress. Note that in the figures below the parties have almost converged on the second DW-NOMINATE dimension. Voting in Congress is almost entirely one-dimensional. The first dimension now accounts for over 93-94 percent of the roll call votes.

Click images to enlarge

House: Vote on $1.1 Trillion Spending Bill (the “Cromnibus”)

Below we use Optimal Classification (OC) in R to plot the House’s 219-206 vote on a $1.1 trillion spending package (the so-called Cromnibus). The vote split both party caucuses, with House Republicans voting 162-67 in favor of the bill and House Democrats splitting 57-139 against it.

The bill angered ideologues on both sides, and the result was a “two-ends-against-the-middle” vote in which a coalition of more moderate Republican and Democratic legislators united to pass the measure. The mean first dimension (representing liberal-conservative position) score of Democrats who voted Yea is -0.41, compared to a more liberal mean score of -0.49 for Nay Democrats (p < 0.01). The mean first dimension score of Yea Republicans is 0.38, compared to a more conservative mean score of 0.44 for Nay Republicans (p < 0.01).

Click image to enlarge

Note: The plot show only 217 Yea and 203 Nay votes because several newly-elected members have not yet cast enough votes to be included in the scaling.