The Effect of Convenience Voting on Election Outcomes: Evidence from a Natural Experiment

Voting-by-mail (VBM) provides voters the opportunity to cast ballots without being exposed to the information revealed in the final weeks leading up to Election Day. We assess whether the resulting informational differences between VBM and polling place voters affect electoral outcomes. We overcome the identification problem caused by the self-selection of voters into VBM by exploiting a natural experiment in the 2008 California presidential primary in which some precincts are assigned to be VBM-only based on an arbitrary threshold of the number of registered voters. Using a regression discontinuity design we show that VBM both increases the probability of selecting withdrawn candidates and affects the relative performance of candidates remaining in the race. Our findings have implications both for public policy and for the study of campaign events and momentum in American elections. 3 On the evening of September 30, 2004, George W. Bush and John Kerry met for the first of their three presidential debates. A Newsweek poll of registered voter