In a post written right after the 2010 election, I found that, other things equal, a Republican candidate affiliated with the Tea Party did about 1.3 points better than one who did not have this affiliation. Now, some more thorough research is beginning to emerge. Here is a newly published article (pdf) by Chris Karpowitz, Quin Monson, Kelly Patterson, and Jeremy Pope. Here is a new working paper (pdf) by Michael Bailey, Jonathan Mummolo, and Hans Noel. I’ll summarize a few findings of note.
Both papers measure a politician’s potential connection to the Tea Party in different ways. What is remarkable is how poorly these different measures correlate with each other. For example, Bailey et al. gather data on the number of Tea Party activists in their district (from here), membership in the Tea Party Caucus, endorsements from FreedomWorks, the Tea Party Express, and Sarah Palin. If they were perfect predictors of each other, the correlations would be 1.0. If they were unrelated, the correlations would be 0. The correlations range in absolute magnitude from 0.02 to 0.32. Thus, as we might expect from a decentralized movement, there is not a lot of coordination among its constituent groups.
Several of these measures predict how Republican candidates fared in 2010. In the primaries, Karpowitz et al. find that GOP candidates endorsed by FreedomWorks or Palin, as well as candidates who signed the “Contract from America,” did better. This evidence is supported by surveys of Republican convention-goers in Utah and Republican primary voters in Colorado, which show that Tea Party supporters were more likely to support the Tea Party-affiliated candidates (i.e., not Bennet in Utah, and Ken Buck in Colorado).
In the general election, Bailey et al. finds that number of Tea Party activists appears to help Republican candidates in 2010 (but not in 2008, suggesting that the 2010 effect is not spurious). Tea Party caucus members actually did slightly worse, although this appears to be a chronically true of these members and thus predates their joining the caucus. Candidates endorsed by FreedomWorks did slightly better, although this could reflect FreedomWorks’s focus on promising candidates. By contrast, almost any other endorsements–by Sarah Palin, the Boston Tea Party, the Tea Party Express–did not appear to help or hurt GOP candidates.
Bailey et al. also uncover apparent Tea Party effects on roll call votes, including budget resolutions and an extension of the Patriot Act. But there is variation in which measures of Tea Party affiliation are associated with these votes, suggesting no simple story on how the Tea Party comes to influence legislative behavior.
I’ll report on more research as it comes available. If readers know of other studies, please leave a note in the comments.