The notion that 20% of Biden voters would’ve voted for Trump if Sanders were the nominee, as well as the notion that 20% of Trump voters would’ve voted for Sanders if he were the nominee are both ridiculous, in my opinion. Feelings about Trump were largely baked in, and the number of Biden>Trump>Sanders and Sanders>Trump>Biden voters is tiny at best (the former is overrepresented quite a bit on this forum.) Sanders would’ve done roughly the same, maybe he would’ve barely lost GA (just barely), but downballot races would’ve gone down similarly, give or take a seat or two. People are letting their feelings get the best of them when it comes to their analysis, unsurprisingly.
Probably AZ too.