Below we use Common Space DW-NOMINATE scores to compare polarization in the current (114th) and previous Congresses. Common Space scores permit comparability across time and between the House and Senate.

The distribution of the ideological (first dimension) scores of the House and Senate Democrats and Republicans in both Congresses are shown below, with the mean scores of members in both parties and chambers marked in the plot.

The results indicate that polarization (i.e., the ideological distance between the two parties) has increased slightly in the House, but has decreased slightly in the Senate. The entry of freshman Republicans such as Senators Mike Rounds (R-SD) [with a score of 0.189], Ben Sasse (R-NE) [0.277], and Dan Sullivan (R-AK) [0.285] has moved the Republican Senate mean slightly to the left in the 114th Congress. In the House, both the Democratic mean and the Republican mean have moved away from the center, but only slightly. The long-term polarization trends in both chambers are shown in the second plot.

These images are from a new (nearly) stand-alone Common Space DW-NOMINATE program that can be run weekly as new roll calls are cast.

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