Open primaries do little to encourage candidate moderation

Many blame the ongoing polarization of Congress on the system of primary election that often rewards the most extreme candidates on either side. But are “open” primaries, where more than just regular partisans can participate the solution to this polarization? Using data from two decades of state-level experimentation with primary laws, Eric McGhee finds that primary races that are “pure closed” can actually result in candidates that are slightly closer together ideologically than those that are “pure open”. Despite this, California has found some success with open primaries increasing moderation among party nominees, and it may well signal the conditions for success.