Group-Based Voting in Multicandidate Elections

Abstract

We study the properties of the group-based model of voting in elections with more than two candidates. We consider two of the most widely used electoral rules around the world: plurality and majority runoff. We fully characterize the set of equilibria under both rules and identify the features of an election that favor different types of voting behavior: either sincere voting or coordination behind a limited number of candidates. Comparing plurality and majority runoff, we find that the incentives to vote sincerely are stronger under the latter, in line with empirical evidence. Our analysis uncovers several strengths of the group-based model of voting: it is tractable, the predictions are empirically sound, and, due to equilibrium uniqueness for a broad set of parameter values, quite crisp. Some results appear sensitive to the composition of groups in the electorate, highlighting the structure of group identity as a key determinant of voting behavior.