Surge and Decline: The Impact of Changes in Voter Turnout on the 2010 Senate Elections

Enthusiasm among Republican voters and a lack thereof among Democrats was cited by many post-election analyses as a contributing factor to the outcome of the 2010 midterm elections. Analysis of the aggregate county level voter turnout and results of the 2010 Senate races provides strong evidence of (1) a sharper decline in turnout from 2008 to 2010 in areas in which Barack Obama did well in 2008 and (2) a significant relationship between turnout changes from 2006–2010 and 2008–2010 and changes in the vote share of Democratic Senate candidates in 2010. In addition, a test of the referendum theory of midterm elections shows that declining presidential approval ratings, but not economic indicators, are predictive of the Democratic vote share in 2010. Despite previous findings that midterm and presidential electorates do not fundamentally differ, this analysis of the 2010 Senate elections provides evidence that differential turnout among core and peripheral voters is an important part of the explanation for the surge that occurs in presidential elections and the subsequent decline in voter participation during midterms.