I think the Dems don't care about Biden one bit. They only care about beating Trump, and finding the candidate who can do that. If in their estimation that's Biden, then they'll support him 100%. If it's someone else, they'll support that person100% with zero concern for Biden.
In the wake of the debate, it almost seemed like the party, meaning the klowns at the DNC wanted him out, but elected Dems (governors, senators, etc.) wanted him to stay. The support from the elected Dems seems to be eroding as time passes.
My theory all along has been that the debate would indicate what the Dems wanted to do with Biden. If they wanted to keep him, he'd come out all amped up like he was at the SOTU address. If they wanted to get rid of him, they'd send him out there with no meds, which looks to have been the case.
Why else would they schedule the debate so early before the actual election? Is there an advantage for them by doing that? If they thought it was to their advantage, I'd have to think there's more to it than early voting.