Biden has lost ground after the debate, but he hasn’t completely cratered. Why? Because the blue team is far more motivated by its fear of Trump than by its feelings for him. People like me will vote for him in spite of his increasingly obvious infirmities because the alternative is so awful. No imaginable set of facts can change that.
But the election will be decided by a few million independent voters who are motivated primarily either by the state of the economy or by their perceptions of which clearly dreadful candidate is less unacceptable. Biden lost a large percentage of the latter category by his performance at the debate. It is unlikely that he can do anything to win them back. That means his only chances of winning the election are some sort of complete Trump meltdown or a remarkably positive change in the condition of the country. Will lower interest rates do the trick, by creating euphoria among investors? How about a cease-fire in the Middle East? I doubt it, but maybe.