California and Washington adopted the "top-two" primary system to combat uncompetitive districts and elect moderates. This change allows same-party candidates to challenge each other before the general election.

Key Finding: Same-party competition in primaries leads to more moderate legislators being elected across partisan districts.

Using data from 2008-2014 elections, this study demonstrates that districts with top-two systems electing via general-election same-party challenges produce significantly more moderate winners than non-competing districts.

However: Elite actors can strategically avoid these challenging primaries, limiting the overall moderating effect observed in broader political outcomes.

This research clarifies how institutional changes like the top-two primary impact candidate selection and demonstrates that policy effects depend on actor behavior.