That elections are all about turnout. It is palpably ridiculous. Hillary lost because swing voters did change their minds. The fact that there were huge number of late undecideds in 2016, compared to very few in 2012, and an in-between number this year serves in itself to discredit Rachel Bitecofer's chief thesis. Comey altered history in 2016 because he impacted preference, not turnout.
Anyway, Biden is in very good shape but the mistake Charlie Cook and others have made is assuming Trump cannot make up ground in significant categories from 2016. That is blatantly wrong. I posted years ago that Trump would fare better than expected with Hispanics in 2020, simply because Hispanics always have strange loyalty to a presidential incumbent. Trump also figures to make up ground with ideological partisans. He got only 81% of the conservative vote in 2016, losing 5% to Gary Johnson in one state after another. In fact, the reason Trump won Pennsylvania and Wisconsin is that he did not suffer nearly as much crossover loss in those states. Trump managed 85% in those two states. If it had been the national number of 81% or even as low as 83% he would have lost both states.
We have to expect Trump will receive at least the 84-85% range nationally this year among conservatives. That's why all the anecdotal stuff means nothing regarding certain Republicans endorsing Biden. We may have heard those names but the overall trend is going to be the other way.
Swing independents will decide this election. That is the type of voter Rachel Bitecofer tries to pretend does not exist. Meanwhile, Independents went for Trump by 4% in 2016 then favored Democrats by 12% in the 2018 midterm. Independents moved away from Trump early in 2017 and have remained in our camp by roughly 10% margin. It really is the only category that means anything. If Biden retains a healthy edge among independents he'll be fine. If not we're on the way to fascism. Turnout means squat compared to preference among independents.