Sincere favorite criterion
Criterion that prevents lesser-evil voting / From Wikipedia, the free encyclopedia
The sincere favorite or no favorite-betrayal criterion is a property of some voting systems, that says voters should have no incentive to vote for someone else over their favorite.[1] It protects voters from having to engage in a kind of strategy called lesser evil voting or decapitation (i.e. removing the "head" off a ballot).[2]
Most rated voting systems, including score voting, satisfy the criterion.[3][4][5] By contrast, ranked choice voting (RCV), traditional runoffs, plurality, and most other variants of ranked voting (including all strictly-Condorcet-compliant methods) fail this criterion.[4][6][7]
Duverger's law says that systems vulnerable to this strategy will typically (though not always) develop two party-systems, as voters will abandon minor-party candidates to support stronger major-party candidates.[8]
Ranked-choice voting fails the favorite-betrayal criterion whenever it fails to elect the Condorcet winner, a situation referred to as a center-squeeze.