Mutual Party Extremism

With four political candidates competing first in two primaries and then in a general election, even a modestly polarized electorate can sustain (in equilibrium) much more extremist candidates. However, a party can sustain extremism only if the other side is extreme, too. A small moderation of one side’s voting electorate can trigger a discontinuous collapse of candidate extremism on both sides — a “moderation export” effect. The converse is also true: minute increases in voter polarization on the more moderate side can trigger radical candidate extremism on both sides. Principled candidates can destroy party electability. Distance-related voter abstention favors extremism.