My ignorant opinion:
- elections are state and local
- ballots are state and local
Remember that it was SCOTUS that shot down the attempts by many states to impose term limits on their own members of Congress, so clearly it is not reluctant to step into things impacting federal office holders. It also was the Supreme Court that shutdown the ability of states to have one house of their own legislatures based on counties (kind of like the Senate...) rather than by population. So while the actual mechanics of an election are general controlled by the states, the Feds definitely have played a major role.
With that being said, I believe there's a near zero chance that the Supreme Court permits individual states to make independent determinations about whether a particular candidate engaged in an insurrection against the
federal government. The idea that different states could reach different conclusions on that, with perhaps some being in bad faith simply to exclude disfavored candidates, is the exact opposite of the kind of consistent legal interpretations the Supreme Court wants on matters of federal importance.
So, it is my opinion that SCOTUS will strike down those state actions, essentially on the grounds that it is not within the purview of the states to determine whether or not a candidate has engaged in an insurrection against the federal government. I believe it most likely that the court will point to section 5 of the 14th Amendment, which specifically references Congress's right to pass enforcement legislation. The Court may determine that such legislation does not exist, and therefore nobody can lawfully be barred from office for insurrection. Or, it may determine that the World War II era law passed regarding insurrection and rebellion, which can be found at 18 USC 2383, is the proper vehicle. But because there has not been a conviction under that statute, nobody can be barred from office.
I personally think that relying on 18 USC 2383 is the cleanest route for the Court. If an individual was convicted under that statute, and the conviction was upheld on appeal, then a state could rely upon that conviction in barring someone from federal office. If the court goes that route, I expect they will drop a footnote saying they are not opining on the constitutionality of that act as a whole, because I think the language in that Act is broader than that under the 14th Amendment and would be unconstitutional to that extent.
It is possible that the court will decide the case by concluding that the prohibition does not apply to the office of the presidency. In some ways, that makes a lot of sense because of the president is the head of the government, so how can he commit an insurrection? In my view, a president could not commit an insurrection until after staying in office past the point where his term legally expired.