As a followup to my skepticism that William Galston and Elaine Kamarck are right to think that open primaries will empower moderates, let me note some evidence that comes my way via John Sides:
— Eric McGhee, Seth Masket, Boris Shor, and Nolan McCarty find “The results of this analysis suggest that the openness of a primary election has little effect, if any, on the partisanship of the politicians it produces.”
— And Eric McGhee alone “This study has examined the available roll-call evidence to determine the effect that open primaries have on representation. The results suggest that most of these systems have little effect on moderation.”
— Stephen Ansolabehere, John Mark Hansen, Shigeo Hirano and James M. Snyder find “The role of primaries as a venue for robust contestation, however, was short-lived, as the competitiveness of federal and statewide primaries decreased sharply starting in the 1940s.”
Primary challenges are rare, and turnout in primaries is low. Those reasons, it seems to me, explain why primary system dynamics in practice have few consequences for political outcomes. I think the reform that anti-polarizers are looking for is multiple member House constituencies so that we’d have one or two Republicans from New York City, a smallish block of white southern Democrats, a conservative Mexican-American from Texas, etc. Then I think you might find that voting patterns became a bit less systematically correlated.