Virtually none of my friends and neighbors who voted for him in 2016 will ever vote for him again. It was a mistake. We should have voted for Hillary. I'd personally expect him to do worse in Ohio than he did last time, against generic D candidate.
I'm not following your logic here.
How was voting for Bernie in the primary a mistake? That would only make sense if he won the nomination and then lost in November (and even that is arguable as being a "mistake").