Extreme Districts, Moderate Winners: Same-Party Challenges, and Deterrence in Top-Two Primaries

Document Type


Publication Date



In an effort to break the link between districts' lack of competitiveness and the election of ideologues, Washington and California recently adopted the “top-two” primary election system. Among other features, the top-two primary allows members of the same party to run against one another in the general election. Although proponents argue that this system encourages the election of more moderate candidates in highly partisan districts, early reports have uncovered mixed evidence of this effect. This study addresses this puzzle by first disentangling the conditions under which one should expect such primaries to encourage the election of more moderate candidates. Using election returns data from the 2008 through 2014 elections, I find that districts facing same-party general-election competition do elect more moderate legislators than similar districts not subject to same-party competition. However, using an application of a common regression discontinuity diagnostic test, I also find that elite actors appear able to strategically avoid this kind of competition—partially explaining why broader effects of the top-two have not been uncovered. The findings contribute not only to ongoing debates about the effectiveness of the top-two primary, but also to our understanding of how political elites may maneuver institutional changes to their own benefit.




Cambridge University Press

Publication Information

Political Science Research and Methods