The unanimous opinion is here.
I had always read Supreme Court cases like Tashjian and CA Democratic Party v. Jones as standing for the principle that if the party objects to the open or closed nature of a primary, it is unconstitutional for the state to use that form of the primary for that party.
But today’s opinion says it is up to the party to provide actual evidence that the law severely burdens the party, namely with “evidence showing a ‘clear and present danger’ that adherents of opposing parties determine the Democratic Party’s nominees.”
This may not stand. First, I’m not sure the Supreme Court would agree such evidence is necessary. Second, the standard seems wrong. Suppose the evidence shows that open primaries lead to more moderate candidates (that’s a contested point, I know) and the party does not want to nominate more moderate candidates. Isn’t that a big burden too?
So keep an eye on this case.