Guest post at The Monkey Cage from Doug Ahler, Jack Citrin, and Gabriel Lenz. Their conclusion: The open primary isn’t producing more moderate candidates because voters can’t tell if candidates are moderates or extreme:
For advocates of the reform, the results of this survey experiment are disappointing. If the open ballot did indeed help moderate candidates, they should have won more votes in the open-ballot condition than in the closed-ballot condition. But as shown in the scatterplot below, we find no such evidence: Moderate candidates for the House of Representatives fared no better under the top-two primary than they would have in closed party primaries.