I watched it all, and Biden did a much worse job than Trump did. Trump lied his way through the whole thing, but we expected that going in. I don’t think Democrats expected Biden to look this feeble.
No, not many people are going to change their vote because of this. But the last few elections have been one with very close margins in a handful of states. It doesn’t take that many people in certain zip codes to decide they can no longer support Biden to turn the election. They don’t even have to turn to Trump, they can go third party or stay home.
I’m not a fan of replacing Biden this late in the process, if that happens for any reason other than Biden’s health then it basically renders all the Primaries invalid, and puts party officials in a position to make the decision, not voters. And let’s be fair: Democrats who were watching saw that Biden was actually able to make his points, and draw a clear distinction between his positions and his opponent. Nobody is saying that the substance of Biden’s performance was wrong, they’re all just upset over the optics of his performance, and his ability to attract those last few voters in PA and WI that he needs.
I recall thinking that Biden lost the first debate in 2020, also. He managed to come back then. We’ll see about this time.