Though partisan polarization has increased dramatically in both chambers of Congress over recent decades, it has beenmore pronounced in the House than the Senate. There is reason to believe that yesterday’s midterm elections will narrow this gap, increasing the ideological distance between Democrats and Republicans in the 114th Senate.
Below we use DW-NOMINATE Common Space scores to plot the ideological positions of members of current, 113th Congress. We use Common Space scores because they allow for direct comparability between members of the House and Senate. The ideological distributions of Democrats and Republicans in the House are shown with the light blue and red lines, while Senate Democrats and Republicans are plotted using the dark blue and red lines.
We highlight the ideological locations of the nine Senate Democrats whose seats flipped (or are likely to flip) to Republicans: Senators Mark Begich (D-AK), Mark Pryor (D-AR), Mark Udall (D-CO), Tom Harkin (D-IA), Mary Landrieu (D-LA), Max Baucus (D-MT), Kay Hagan (D-NC), Tim Johnson (D-SD), and Jay Rockefeller (D-WV). We can also plot the positions of five of the Republican Senators-elect (or, in Louisiana, the front-runner for the December 6 runoff) who have served in the House and have comparable Common Space scores: Reps. Tom Cotton (R-AR), Cory Gardner (R-CO), Bill Cassidy (R-LA), Steve Daines (R-MT), and Shelley Moore Capito (R-WV).
The 2010 midterms devastated the ranks of moderate Blue Dogs in the House. To a lesser degree, the 2014 midterms will have a similar effect on the Senate Democratic Caucus. Six of the Democratic Senators shown are among the seventeen most moderate Democrats in the current, 113th Senate (using the Common Space scores). With the exception of Senator-elect Shelley Moore Capito (R-WV), their replacements do not appear to be symmetrically moderate. The other four Republican Senators-elect for whom we do not have ideological scores (Dan Sullivan in Alaska, Joni Ernst in Iowa, Thom Tillis in North Carolina, and Mike Rounds in South Dakota, seem likely to be at least as conservative as the median member of their party’s caucus). Indeed, the freshman Republicans in the 114th Senate appear primed to move their party’s distribution closer to that of House Republicans.
Click image to enlarge