Other than dropping out of the race, what should Biden do to recover from his bad debate?

The problem is how to do that and who replaces him? I think it is easy enough to say he's bowing out do to medical reasons after talking to his doctors and family. It can even be framed as he is doing this for the good of the country, which might be enough to explain how picking another candidate isn't against the voters wishes. It would be the same as if he died and the dems had to pick another candidate. The obvious choice is Harris since she is the VP, but she has been in the shadows long enough that she doesn't have a positive presence. So if Harris is going to have a chance, Biden needs to drop out NOW so she has a chance to present her case and build an effective campaign before the convention.

Whitmore is probably the best choice as VP, but (and I hate this actually needs to be taken into account) a 2 women ticket is very risky. Next best would be either Ossoff or Fetterman to pull some swing states. But this assumes Harris is able to pull together a campaign in time for the convention. Whitmore and Warnock should be put forth as potential replacements early on and be ready to jump in at the convention if needed.