Aggregate Uncertainty in Runoff Elections

I develop a model of strategic entry by candidates for office in runoff elections under aggregate uncertainty. I introduce aggregate uncertainty by making candidates unsure of the distribution of voter preferences in the electorate. The set of three candidate equilibria expands and equilibrium platforms become more diverse. These results provide a theoretical basis for Duverger's Hypothesis, the claim that runoffs encourage entry by more than two candidates. Three candidate equilibria also feature three common empirical phenomena that existing literature fails to generate. First, some candidates choose to enter despite losing with certainty. Second, in some equilibria, a Condorcet winning candidate fails to win the election, and a Condorcet losing candidate wins with positive probability. Finally, some candidates who reach the second round may receive fewer votes than they receive in the first round. Comparative statics generated by the model are confirmed in data from Italian municipal elections