This post is jointly authored with Boris Shor of the University of Chicago’s Harris School (currently Robert Wood Johnson Scholar at UC Berkeley).
As election day draws near, there has been growing interest in just what sort of 113th Congress we might expect to emerge. Will it be more polarized and ideological than the 112th or less? The Washington Post’s Aaron Blake has speculated that redistricting will lead to a more polarized House by drawing fewer competitive seats. This idea received some pushback from two of Monkey Cage’s finest: first from John Sides, then from Nolan McCarty, both of them citing McCarty’s own research with Keith Poole and Howard Rosenthal pointing to only a modest effect from redistricting.
Boris recently offered a way to assess these claims for the current election cycle. He has calculated the estimated ideological position on the liberal-conservative spectrum (“ideal point” is the jargon) for at least one candidate in almost every House and Senate race this cycle. (See here for details about the data and his methodology, and here for the scores.) This includes estimates for 722 House candidates from 419 districts and 64 Senate candidates from 33 states with elections this year.
We have combined his data with the partisanship of the congressional districts, measured with the 2008 presidential vote in these districts (the numbers are from Daily Kos). We wanted to know whether the partisanship of the district is at least correlated with candidate ideology, and how a candidate’s party label plays into all that.
The main take-away: party trumps constituency. The ideological differences between Republicans and Democrats are much larger than the differences between candidates running in Republican and Democratic districts.
As one would expect, candidates get a bit more liberal as Obama’s share of the 2008 vote increases. But the difference is surprisingly modest. Moreover, the gap between the parties is vast at every point along the way, and overwhelms this modest relationship.
There are also some interesting nuances. First, extremists and moderates can be found almost everywhere. There are some relatively moderate Democrats in heavy Obama districts, and some moderate Republicans in districts that went strong for McCain. Keep in mind that these ideologies are based on each candidate’s positioning in the campaign. Measures of elected legislators’ voting behavior in office generally show far fewer moderates. This suggests that, either by design or due to pressures beyond their control, candidates often campaign as moderates and govern as partisans. We’re not the first to make this point — see here (gated) — but it’s interesting to see it confirmed.
Second, just because the partisan gap is large doesn’t mean the parties are completely unified. In fact, within each party caucus there are two distinct camps, one much more extreme than the other. At his own blog Boris has offered more detail on this pattern. This suggests more division within the parties—both its winners and its losers—than is often recognized.
Third, eyeballing the chart makes it look like both factions of Democrats and the moderate faction of Republicans are at least somewhat responsive to district partisanship. But the conservative Republican faction at the top of the graph is flat. So some Republicans appear to be immune to the even modest pressure imposed by district realities.
Despite these nuances, however, the overall point is that the parties differ drastically. McCarty offers perhaps the best summary: “polarization has grown because Democrats and Republicans are representing moderate districts in increasingly extreme ways.” We can add that this appears to be true in all the other districts, too.
(Note: The original post incorrectly referred to the current Congress as the 113th, and the next one as the 114th.)