You didn't specify his VP pick as a factor. If it's Harris again, voters will have to seriously decide if they want her to be president -- either when Biden is incapacitated or when she runs in 2028. Given her lack of track record the last couple of years, she's going to have a hard time with that.
I think you're forgetting who their voter base is. To them, results don't matter as we've seen how quickly things can change going from Trump to Biden. Even when this affects everyone, they still would vote for Biden. See my dads example. When I say affects, I mean in a bad way. Of course higher gas impacts everyone, but for people who can afford it, they don't care. Like my dad. His statement "well, good thing I can afford it" when I brought up the higher gas prices and why they increased.
Then the multiple hoax's and they still believe what's being told to them on the news, even though it's been and is pointed out that it's wrong and why. I would get into heated discussions about Russia early on with my dad. Pointing out all the logical falsehoods about it. But nope, he says something along the line "you're not the expert, there are people investigating who know way more". But fast forward to the Mueller report which he dismissed and focused solely on that "this doesn't exonerate Trump". Even after I pointed out an investigator doesn't exonerate people, the court does (judge/jury).
So that's why I say Harris could still be picked as VP and it won't have much affect like how a competent voter would. Cause a competent voter wouldn't vote for Biden at all.