Group-Based Voting In Multicandidate Elections

We study the properties of the group-based model of voting in elections with more than two alternatives. In that model, voters coordinate at the group level rather than making decisions at the individual level. We characterize the set of (pure strategy) equilibria under two of the most widely used electoral rules around the world: plurality and majority runoff. There is a unique equilibrium for a broad range of parameter values. We identify the features of an election that lead to different types of voting behavior: either sincere voting or coordination behind a limited number of candidates. Our model thus clearly predicts when Duverger's law will fail. Comparing plurality and majority runoff, we find that incentives to vote sincerely are stronger under the latter, in line with empirical evidence. A distinguishing feature of the group-based voting model is that, even in large elections, cardinal utilities shape voting behavior.