Bandwagons and Momentum in Sequential Voting

In this paper I show that an equilibrium exists to the sequential voting game in which a bandwagon begins with probability one. These bandwagons are driven by a combination of beliefs and the desire of voters to vote for the winning candidate. Signi...cantly, in this equilibrium the pivot probability for each voter is nonzero, even in an in...nite population. Consequently the bandwagons do not always start after one (or at most two) favorable decisions (as do economic cascades) and varying levels of informative voting are observed, consistent with observations from sequential voting in U.S. presidential primaries. Further, voters are exposed to counterintuitive incentives, referred to as “buyers’ remorse,” that have been attributed to real primary voters. From the play of this equilibrium an explanation of momentum arises that is consistent with empirical regularities. This interpretation provides a formal distinction between the often ambiguous concepts of momentum and bandwagons, and permits a separation of their e¤ects on the sequential voting mechanism. ¤Assistant Professor of Managerial Economics and Decision Sciences at the Kellogg School of Management, Northwestern University, Evanston, IL 60208; [email protected]