Center squeeze - Wikipedia

In social choice, a center squeeze is a kind of spoiler effect common to plurality-elimination rules like the two-round system, plurality-with-primaries, and ranked-choice voting (RCV).[ 1] In a center squeeze, a majority-preferred and socially-optimal candidate is eliminated in favor of a more extreme alternative.[ 2] [ 3] Extreme or polarizing candidates who focus on appealing to a small political base can thus "squeeze" broadly-popular candidates trapped between them, starving them of the first preferences they need to survive early rounds.[ 1] [ 4]

The term "center squeeze" refers to candidates who are close to the center of public opinion, and as a result is not limited to centrists along the traditional political spectrum.[ 5] Center squeezes can occur in any situation where voters prefer candidates who hold views similar to their own.[ 6] By Black's theorem, the candidate who appeals most to the median voter will be the majority-preferred candidate, which means they will be elected by any method compatible with majority-rule.[ 1] [ 2] However, in methods that strongly prioritize first preferences, these candidates are often eliminated early on because they aim for broad appeal rather than strong base support.[ 1] [ 7] [ 8]

Voting systems that suffer from the center-squeeze effect incentivize candidates to avoid the political center,[ 4] [ 9] creating political polarization in the long run.[ 7] [ 9] [ 10] As a result, rules like RCV can lead to extreme winners even if center-squeezes seem empirically rare, because the rules disincentivize moderates from running for office in the first place.[ 9] [ 11] [ 12] The effect was first predicted by social choice theorists in the 1940s[ 13] before being confirmed empirically in Australia,[ 11] [ 14] [ 15] California,[ 16] [ 17] and Maine,[ 18] and is well-known for causing polarization through the American primary election process.

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