Center squeeze: Difference between revisions
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The '''center squeeze effect''' refers to a class of voting scenarios which are troublesome for many voting systems. In such a scenario, the strongest three candidates can be arranged on a spectrum such as "left", "center", and "right"; and of the three, the "center" candidate is the [[Condorcet winner]] or [[utilitarian winner]], but loses the election.<ref>{{Cite journal|last=Lewyn|first=Michael|date=2012|title=Two Cheers for Instant Runoff Voting|url=https://papers.ssrn.com/abstract=2276015|language=en|location=Rochester, NY|journal=6 Phoenix L. Rev.|volume=117|pages=|via=|quote=third place Candidate C is a centrist who is in fact 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}}</ref><ref>{{Cite journal|last=Merrill|first=Samuel|date=1984|title=A Comparison of Efficiency of Multicandidate Electoral Systems|url=http://dx.doi.org/10.2307/2110786|journal=American Journal of Political Science|volume=28|issue=1|pages=23|doi=10.2307/2110786|issn=0092-5853|quote=However, squeezed by surrounding opponents, a centrist candidate may receive few first-place votes and be eliminated under Hare.|via=}}</ref><ref>{{Cite journal|last=Merrill|first=Samuel|date=1985|title=A statistical model for Condorcet efficiency based on simulation under spatial model assumptions|url=http://dx.doi.org/10.1007/bf00127534|journal=Public Choice|volume=47|issue=2|pages=389–403|doi=10.1007/bf00127534|issn=0048-5829|quote=the 'squeeze effect' that tends to reduce Condorcet efficiency if the relative dispersion (RD) of candidates is low. This effect is particularly strong for the plurality, runoff, and Hare systems, for which the garnering of first-place votes in a large field is essential to winning|via=}}</ref>
Most consider that if the center candidate is not too far behind in honest plurality, they should be the winner, as they would beat any other candidate in a head-to-head election, and otherwise, the voting system is encouraging strategy (typically, a favorite betrayal) from one of the other two groups. (Though note that any voting method avoiding center squeeze can also incentivize strategy if one of the wings thinks they can squeeze out victory for their preferred candidate i.e. if the "liberal" wing bullet votes in Approval voting).
(Note that "center" does not refer to an absolute political spectrum, but relative to the ideologies of the candidates. If the Libertarian Party holds an election, for instance, the winner should be near the center of Libertarian ideology, but if there are other candidates to either side, the most-representative candidate cannot win.)
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