I've been comparing Bernie Sanders to the Tea Party, in part because he rejects the legitimacy of his opposition (see here), and the basis of his claim against Clinton is that "closed" primaries are intrinsically illegitimate. Political science time!
Let's start with the definitions. A closed primary is one in which only voters registered with a party may vote in that party's primary. An open primary is one in which you can choose to vote in either party's primary, regardless of your registration. The motivation for the open primary is that it is supposed to reduce polarization. The idea is that if Democrats and independents vote in a Republican primary, that pulls Republicans towards the center, just as if Republicans and independents vote in a Democratic primary, that pulls Democrats towards the center.
Does it work? The jury's out on that one, but the effects are somewhere in the range between small and non-existent. But here's the irony. Sanders is the extremist, but he did better in the states with open primaries. It ain't supposed to work that way! Why did Sanders do better in the states with open primaries? We don't know yet. I'll wait for the academic work on the subject. At this point, we mostly have speculation and a smattering of poll results that are hard to look at across state lines.
But then there's that legitimacy question. Imagine that Sanders had done better in the closed primary states, but Clinton won overall. Would Sanders accept those results because open primaries are better? You know the answer to that one. Of course he wouldn't. Nobody has coherent preferences on this kind of procedural matter. It is too tempting to evaluate procedures based on whether or not they give us the outcome we want at the time.
So, imagine that Clinton had done better in open primaries, and won overall. Sanders' argument would go as follows: Clinton is an illegitimate nominee because she only got the nomination from Republicans meddling in the Democratic contest. Democrats are the ones who should be picking the Democratic nominee.
In fact, we don't have to imagine this because Sanders has already essentially made that argument. Sanders tried to dismiss Clinton's victories in Southern states because Southern states are Republican, making those delegates illegitimate. Of course, Clinton did better in Southern states because the Democrats in Southern states are largely African-American, and Clinton has done better with African-Americans than Sanders. Sanders' argument was nonsense, obviously, but the fact that he made it demonstrates what he really thinks about open and closed primaries. The form that is legitimate is the one that helps him.
Are there any coherent arguments on open versus closed primaries? Only weak ones. Perhaps that is the subject of another post. The point here is that we should be puzzled that the extremist did better in the open primary states, and cognizant of the fact that said candidate both complains about the exclusion of independents and Republicans from the closed primary states while also dismissing his opponent's victories in Republican-leaning states.