If you ask me, and no one has, the Democratic Party would be foolish to replace Joe Biden at this point in the game.
Yes, he's suffering from memory loss and is clearly, visibly, unfit to continue in office. But that didn't start when the media lifted its self-imposed blinders after the debate; the general public knew the emperor had no clothes for at least a year now. The time to get a healthier, more viable option was back when the primary season began.
Now? With a convention coming up and the election what, 100 days away? Changing horses now just tells the voters you either didn't pay attention or didn't care when you should have, and leaves the public trying to evaluate and trust a new candidate at the 11th hour.
Not to mention a contested DNC convention in Chicago should spark some superstition.
I do NOT buy into the argument that a Biden-Trump matchup is an automatic loss for Biden. That is media hysteria as rooted in fact as the "The President is fine" nonsense they parroted for the last year. I think he's probably, regrettably, the best option to defeat a second Trump term.
Remove Biden, and I think you seal a victory for Trump. If that's your goal, fine. If it isn't . . . live with your choice.