Duverger's Law and Party Primaries

[SPC]

While in recent years party primaries have tended to gravitate toward two major opponents, why hasn't the phenomenon of several strong candidates, especially in presidential primaries, become less prevalent, given the winner-take-all plurality system?

[SteveRogers]

Duverger's law was never intended to describe primaries. Duverger's law is a prediction about the party system that will result from a set of electoral rules, not necessarily a prediction about the number of candidates that will appear on an individual ballot. What matters is the output of the elections in the various districts in the aggregate.

A partisan primary will always yield only one nominee regardless of how many candidates compete and regardless of whether the winner needs a plurality or a majority. There is no aggregate outcome to consider. Additionally, the underlying psychological effects that discourage minor parties from running candidates in SMD plurality elections don't really apply to weak primary candidates.

[○∙◄☻¥tπ[╪AV┼cVê└]

Splitting the vote isn't as big a deal for primaries since after a candidate drops out they won't be splitting the vote. Also Democratic primaries and early Republican primaries are proportional.