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A center squeeze is a kind of spoiler effect shared by rules like the two-round system, plurality-with-primaries, and ranked choice voting. In a center squeeze, the majority-preferred and socially optimal candidate is eliminated in favor of a more Extremism alternative before having a chance to face another candidate in a one-on-one race. Systems with center-squeeze are sometimes called centrifugal ("center-fleeing") because they encourage political polarization.
Candidates focused on appealing to a small Political base of Core support can "squeeze" broadly-popular candidates trapped between them out of the race, by splitting the first-round vote needed to survive earlier rounds. This effect was first predicted by social choice theorists in the 1940s and 50s, and has since been documented in various countries using plurality-style electoral systems.
Famous examples of center squeezes include the Alaska's 2022 special election (where Nick Begich III was eliminated in the first round by Sarah Palin) as well as the 2007 French presidential election, where moderate liberal François Bayrou was eliminated by left-populist Ségolène Royal, allowing the right-wing Nicolas Sarkozy to win the second round.
By Black's median-voter theorem, the candidate who appeals most to the median voter will be the majority-preferred candidate, which means they will be elected by Condorcet method. However, in methods that strongly prioritize first preferences, these candidates are often eliminated early on because they aim for broad appeal rather than strong Political base.: "third place Candidate C is a centrist who is the second choice of Candidate A's left-wing supporters and Candidate B's right-wing supporters. ... In such a situation, Candidate C would prevail over both Candidates A ... and B ... in a one-on-one runoff election. Yet, Candidate C would not prevail under IRV because he or she finished third and thus would be the first candidate eliminated"
The "center" in "center squeeze" refers to candidates who are close to the center of public opinion , and is not limited to Centrism along a traditional, one-dimensional political spectrum. A center squeeze can occur in any situation where voters prefer candidates who hold views similar to their own.
Center-squeeze has been observed in Australia, Maine, Fiji, and various United States cities, all of which use ranked-choice voting, in addition to California (which uses nonpartisan primaries).
If voters assign scores to candidates based on ideological distance, score voting will always select the candidate closest to some central tendency of the voter distribution. As a result, while score voting does not always elect the candidate closest to the median voter, it often behaves like methods that do.
The opposite situation—a bias in favor of bland, inoffensive, or unknown candidates—is not common in any widely-used voting rules. However, it can occur for "negative" voting methods that choose candidates with the least opposition, like anti-plurality, D21 – Janeček, or Coombs' method.
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| 33.4% | 17.2% | 13.4% | 35.9% |
Because is preferred to both and in head-to-head match-ups, is the Condorcet winner. is the socially-optimal winner as well. Thus, is the "best" or "most popular" candidate under both common metrics of candidate quality in social choice.
The first round of the election is the same as the FPP election. has the least first preferences and is therefore eliminated. Their votes are reassigned to and , according to their ballot. In the second round, enough voters who preferred as their first choice took as their second choice and wins the election. RCV thus fails to have a substantial moderating impact, instead causing only a swing from one extreme to the other.
The election produced a winner opposed by a majority of voters, with a majority of voters ranking Begich above Peltola and Palin, and more than half giving Peltola no support at all. The election was also notable as a no-show paradox, where a candidate is eliminated as a result of votes cast in support of their candidacy. In this case, ballots ranking Palin first and Begich second instead allowed Peltola to win.
Many social choice theorists criticized the ranked-choice runoff procedure for its pathological behavior. Along with being a center squeeze, the election was a negative voting weight event, where a voter's ballot has the opposite of its intended effect (e.g. where a candidate would need more votes to lose). In this race, Peltola would have lost if she had received more support from Palin voters, and won as a result of 5,200 ballots that ranked her last (after Palin then Begich). However, social choice theorists were careful to note the results likely would have been the same under Alaska's previous primary system as well. This led several to recommend replacing the system with any one of several alternatives without these behaviors, such as STAR voting, Approval voting, or Condorcet method.
The election results were criticized by mathematicians and Voting theory for several pathologies associated with RCV. These included a no-show paradox, where Kiss won only as a result of 750 votes ranking Kiss in last place. Several electoral reform advocates branded the election a failure after Kiss was elected despite 54% of voters voting for Montroll over Kiss, violating the majority-rule principle.
: "election where Democratic candidate for mayor was Condorcet winner but finished third behind Republican and 'Progressive,'" Later analyses showed the race was spoiled, with Wright pulling moderate votes away from Montroll, who would have beat Kiss in a one-on-one race.The controversy culminated in a successful 2010 initiative that repealed RCV by a vote of 52% to 48%, a 16-point shift from the 64% who had supported the 2005 ratification. The results of every possible one-on-one election are as follows:
Montroll was therefore preferred over Kiss by 54% of voters, over Wright by 56% of voters, over Smith by 60%, and over Simpson by 91% of voters.
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