The polls which show erosion of support for Trump if he's convicted of a felony - which I'm going to take as conviction in the classified document case or in the federal Jan 6th case - were particularly relevant as they were exit polls of Republican caucus voters.
I agree that 30-35% of Trump's base are MAGA diehards who could care less, but that's not the entire Republican electorate.
You're free to discount the polling if you wish, but I think it's relevant.
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As for what might rescue Democrats absent a Trump felony conviction... numerous factors are in play, particularly abortion. If, in swing states, Democrats are successful in getting abortion rights measures to appear on their ballots, this will have a big impact in turnout of woman voters the vast majority of whom will vote Democrat.
Although it remains to be seen how impactful the House's refusal to take up the bipartisan immigration bill passed by the Senate will be, one would think that the hypocrisy this action lays bare could well sway some few voters.
Then there's the repeated bullshit impeachment attempts that the House keeps trying to pull off. This behavior rankles many folks.
And on and on.
It's really amazing that the race is going to be close. Biden should win this thing by a landslide.