Plurality Versus Majority Election of Presidents

Abstract

Under plurality rule, presidents may be elected with narrow support whenever there are more than two “serious” candidates. Even under majority-runoff rules, the eventual winner may have received the backing of only a small minority in the first round. This article shows that majority runoff rules tend to be associated with an “effective” number of presidential candidates greater than three. The effective number for plurality is, on average, less; however, a nontrivial share of such elections have resulted in close multicandidate races. The article proposes an alternative “double complement rule,” which is derived as the arithmetic average of majority runoff and plurality criteria. This rule stipulates that a front-runner with less than a majority of the votes wins without need of a second round if the shortfall of the runner-up from a majority of votes is more than double the leading candidate's shortfall from a majority. Possible effects and desirable conditions of this rule are assessed in light of the existing debate about electoral methods.