No person shall be denied the opportunity to vote in a primary election for the office of Senator, Representative, President, or Vice-President, on account of his or her party affiliation or lack thereof.He proposes this as a remedy to the problem of excessive party polarization, the logic being that more moderate, independent voters in primaries would tend to produce more moderate elected officials.
I believe such an amendment would be a mistake. I'm actually writing a chapter on this topic right now for CQ's Debating Reform series, so I don't want to give away the store, but I'll provide the basic details of my argument. Mandated open primaries are a bad idea because 1) there's little evidence they would actually reduce partisanship; 2) if they somehow did reduce partisanship, that would actually hurt our political system; and 3) open primaries are fundamentally unfair to those who provide the real labor of parties. I'll deal with these one at a time.
Open primaries don't reduce partisanship
In a study I conducted with Nolan McCarty, Eric McGhee, Steve Rogers, and Boris Shor, we examined the roll call voting behavior of state legislators all across the country over the past two decades based on the openness of their primary election rules. We found no consistent effect of primary rules on legislative partisanship; legislators in open primary states appeared no more or less partisan than those in closed primary states. We even looked at those states (California, Washington, and Alaska) that had blanket primaries (voters can choose among candidates of all parties for any given office) that were forced to change their systems when the blanket primary was ruled unconstitutional. California's legislators only became slightly more polarized; there was no effect in Washington or Alaska.
Why would the primary rules have no effect on partisanship? Well, for one thing, unaffiliated voters tend not to show up for primary elections anyway, even if the rules permit them to participate. For another, party elites have proven very adept at securing the nominations of candidates they like through their allocation of vital campaign resources like endorsements, money, and expertise. They can make sure that a moderate has little chance of winning a primary, even if moderate voters show up to vote.
Now, could a shift in primary rules reduce the partisanship of elected officials? Possibly. Nebraska and Louisiana use a top-two style primary, in which the top two vote-getters, regardless of party, go to a runoff election, and both of those states have relatively low levels of partisanship (although it's hard to say just how much the top-two system is responsible for that). California just had its first experiment with such a primary, and while the initial results were unimpressively different from the past, it is still early to know what kind of effect the system will have on legislative partisanship.
Reduced partisanship has bad consequences
Strong partisanship is admittedly frustrating. But if we could reduce the partisanship of elected officials, would that be a good thing? Not necessarily. Parties do a lot of the important work of a representative democracy for us. Notably, they give voters a opening to weigh in. Most voters have little idea what individual members of a legislature are doing from day to day, but they can evaluate the performance of the majority party, and if they don't like the way things are going, they can vote in a new party. This kind of partisanship brings some accountability to the system. Legislatures with weak or nonexistent parties are often quite collegial, but they do not produce obviously better laws, and they want for accountability and may be more prone to corruption.
Open primaries are unfair
To whom do the primaries belong? Does an independent voter – one who has declined to claim membership in an organized party – have a “right” to pick that party’s nominees? If we were to insist that all states have open primaries, we would be telling all those who have worked for a party, donated to that party, and loyally voted with that party that they have no more claim to picking that party’s nominees than a first-time unaffiliated voter who has no ties to that party at all. Is this right?
Nancy Rosenblum wrote about this debate extensively in her wonderful book On the Side of the Angels. As she notes, our political discourse tends to privilege the independent or unaffiliated voter. Witness, for example, the presidential debates and voter forums to which only independent voters are invited; voters who have made a decision early are deemed to have insufficient standing to participate. But why, in the case of primaries, should the “right” of the independent to participate trump the “right” of the loyal partisan to determine her party’s nominees?
So, to sum up, open primaries don't really do what reforms promise they'll do, it would be bad if they actually did, and they're unfair regardless. Sorry to get all normative.