One of the reforms Senator Bernie Sanders and his supporters have been pushing in recent months is open primaries. Many argue that more open primaries, allowing independents to participate, can produce more moderate nominees that are more representative of the electorate as a whole. Evidence suggests, however, that this doesn’t really happen. Here’s why. The logic of the open primary is pretty straightforward. Under a closed primary, only people who are registered party members (usually for some time) are permitted to vote. Those party registrants tend to be die-hard partisans, and the candidates they pick will tend to be from the ideological extremes. Independent voters, who might legitimately want a more moderate set of nominees, are forbidden from participating. Allow them in, and you end up not only with more moderate nominees, but nominees who recognize it’s in their interests to keep moderate independent voters happy while they serve in office. Eric McGhee, Boris Shor, Nolan McCarty, Steve Rogers, and I tested this assumption in a large-scale study a few years ago. We looked at two decades of voting behavior by state legislators across all 50 states, and we compared legislators based on the type of primary system that nominated them. Quite a few state parties have changed their primary rules one way or another over this time period, allowing us a good deal of leverage on the question.
People unaffiliated with a party tend, on average, to be less interested in politics and less likely to vote.
