Strategic Voting under Plurality Rule: When Does It Matter and Who should Vote Strategically?
Emerson M.S. Niou
Abstract
This paper establishes the conditions under which strategic voting can change the election outcome, and identifies the voters who should vote strategically under simple plurality rule and the runoff rule. Three interesting findings can be drawn from the results. First, under simple plurality rule, strategic voting can change the election outcome only if the plurality winner is not the Condorcet winner or the Condorcet winner does not exist; under the runoff rule, strategic voting can change the election outcome only if the Condorcet winner is the plurality loser or the Condorcet winner does not exist. Second, under simple plurality rule, the Condorcet winner is not always the strategic voting outcome even if we assume that voters have complete information about the preference profile. Even worse, the Condorcet loser could win. Under the runoff rule, however, strategic voting ensures that the Condorcet winner will win if one exists. Third, strategic voting is less likely to occur under the runoff rule than under simple plurality rule.