It's a possibility; they have been acting like they don't care whether then win or lose in this campaign and it has felt like they think it's "a good election to lose" for while.

It just show what a circus/theatre the whole political stage is in the US. Biden is like this all the time, and probably much worse in private, but the way it's all managed means there is limited exposure of it; he's only presented to the public in very small, closely managed, edited, doses. That left them able to claim that anyone bringing up his mental capablity has been condemned as being unfair or a smear artist.

Now they are ALL screaming WTF IS THIS? Too late now. Whoever they bring in has four months to campaign? No chance.