@Vanitas: Folks don't tend to recollect that the late Strom Thurmond was the only Senator ever elected to the U.S. Senate via a write-in campaign. Other candidates for various offices get written in routinely and always have done, and in local and some state offices they have won. The Presidency is not different, really. That said, that Insurrection Clause (or whatever it is) is the trick on this one. Someone could win but be DQ'ed anyway if they were found to have been an insurrectionist.
@Vanitas: Dunno. 🤷♂️
Could be. If so, I was/am unaware.