A majority rule philosophy for instant runoff voting

Abstract

We present the core support criterion, a voting criterion satisfied by Instant Runoff Voting (IRV) that is analogous to the Condorcet criterion but reflective of a different majority rule philosophy. Condorcet methods can be thought of as conducting elections between each pair of candidates, counting all ballots to determine the winner of each pair-election. IRV can also be thought of as conducting elections between all pairs of candidates but for each pair-election only counting ballots from voters who do not prefer another major candidate (as determined self-consistently from the IRV social ranking) to the two candidates in contention. The appropriateness of including all ballots or a subset of ballots for a pair-election, depends on whether the society deems the entire or a selected ballot set in compliance with freedom of association, which implies freedom of non-association, for a given pair election. Arguments based on freedom of association rely on more information about an electorate than can be learned from ranked ballots alone. We present a freedom-of-association based argument to explain why IRV may be preferable to Condorcet in some circumstances, including the 2022 Alaska special congressional election and the 2009 Burlington Vermont mayoral election, based on the political context of those elections.