About that thing that happened
By 
Some thoughts:
(1) It’s important for the sake of sanity not to lose sight of how completely insane all this is. Choosing a president on the basis of last night’s fake debate format is like choosing whether or not to replace the guy who has been a mostly excellent quarterback for the last three and a half seasons on the basis of a hot dog eating contest. Donald Trump is good at lying nonstop on TV, which is to presidenting as eating hot dogs fast is to quarterbacking. Speaking of quarterbacking of the Monday morning variety, debating Trump at all is legitimating him and his cult in a powerful way. It’s like a real historian of the Holocaust “debating” a Holocaust denier, which is a terrible idea for what should be obvious reasons. But our political culture is simply incapable of recognizing Trump and Trumpism for what they are, and I guess it’s not really fair to blame Biden and his people for that fact.
(2) Biden is as stubborn as a mule and isn’t going to drop out, so there’s no point in discussing that. BTW one thing I don’t like is the claim that the ONLY reason somebody might be legitimately concerned about Biden’s age is that he might die suddenly, and the ONLY reason that’s a concern because people are racist and misogynist. A far more compelling reason to be concerned about Biden’s age is slow physical and mental deterioration, that doesn’t ever reach obvious 25th amendment territory. Biden’s evident frailty is a powerful synecdoche for that in the minds of the Ariana Grande vote. That’s just how life works, which as you may have noticed is unfair.
(3) As for how all concerns about Harris are just racism and misogyny, a lot of them are of course, this being America, but I was a Harris fan early in the 2020 campaign season, and her campaign was a wall to wall disaster. Campaigning for president is not the same thing as being president (Joe Biden had two disastrous presidential campaigns), but that face plant — she dropped out two months before Iowa with no money and her staff falling apart — was not an encouraging precedent for somebody with a limited national track record, given that if she were to replace Biden she would have to win a campaign for president before she could be president.
(4) Trump may well now refuse to do the second debate. This would be the smart play, and the only reason he might not make it is that he’s a narcissistic idiot, but from a strategical point of view there’s no reason to give Biden a second bite at the apple.
(5) Tomorrow ain’t promised to no one. Meanwhile, we go on.