In this study, Molly Milligan of the Center for Governmental Studies analyzes voter registration data and recent primary election results to estimate the potential effects of the passage of Proposition 14, the open primary initiative on the June 2010 ballot. Among other findings, her analysis predicts that one-third of congressional and state legislative primary elections could result in general election run-offs between two candidates of the same-party and that the change could make elections more expensive.