Electoral Equilibrium under Alternative Voting Institutions

Abstract

This paper investigates the nature of multicandidate electoral equilibria under three different classes of single-ballot-single-winner voting systems: (1) scoring rules (including the plurality rule, Borda's method of marks, and negative voting); (2) Condorcet completion procedures; and (3) multiple vote procedures (including approval voting). Some of the key findings of the paper are that (1) multicandidate equilibria under the plurality rule must be noncentrist (Theorem 1); (2) in an election held under any Condorcet procedure, candidates have a dominant strategy to adopt the median voter's position (Theorem 4); (3) there is a set of nontrivial voting methods for which equilibria routinely exist regardless of the dimensionality of the policy space; and (4) the plurality rule is alone among commonly discussed voting procedures in not having centrist multicandidate equilibria.