How much did health care matter in Tuesday's results? A lot, argues Eric McGhee; in fact, it may have helped cost Democrats control of the House:
The simplest approach to this question is to compare Democratic incumbents on the ballot who cast votes for these bills to those who didn't. (The roll call vote data are here, although they are gated.) For each Democratic incumbent, I counted how many of these four bills they voted for, and then tabulated the average Democratic vote for each group:
Support for these bills appears to have helped rather than hurt. But of course, Democrats who opposed these bills were more likely to represent competitive or even Republican districts, meaning they did worse for other reasons (see Brendan Nyhan for a similar point). So I modeled Democratic vote share in contested House districts using this count of "yes" votes, plus campaign money in 2010 (from here and here) and each district's House and presidential vote in 2008 as controls (here).1 The model also estimates whether the effect of roll call votes depended on the partisanship of the district, as captured by the 2008 presidential vote. This model predicts a Republican majority of 242 seats, compared to the 244 it currently looks like they are going to win. So the model is pretty good, understating Republican performance only a little bit.
What does this model tell us about roll call votes on these four bills? Simple answer: they mattered. A lot. A Democratic incumbent in the average district represented by Democratic incumbents actually lost about 2/3 of a percentage point for every yes vote. That doesn't sound like a lot, but that's for incumbents in districts that voted 63% for Obama.
For Democrats in the least Democratic districts (Chet Edwards of TX or Gene Taylor of MS), the model suggests a loss of about 4% for every yes vote. Does that mean poor Chet lost 16 points on roll call votes alone? No, because he wasn't a big supporter of Obama's agenda. But he did vote for both TARP and the stimulus. In fact, virtually every Democratic incumbent on the ballot yesterday supported at least one of these four bills. That support was costly.
What might have happened if vulnerable Democrats hadn't voted for any of the four bills? I'll define "vulnerable" as any Democratic incumbent who lost. The graph below shows the balance of power as predicted by the regression, and then what it might have been if everything else was the same but these vulnerable Democrats had voted "no" on everything. The result is stunning . . . Democrats gain back 32 seats, enough to retain control of the House.
I'm still sort of awed that Democrats managed to convince themselves otherwise. It was the Underpants Gnome theory of politics: