100% agree. Biden had a cold, which was unfortunate, though he should have just said. I don't know what to say about that poor performance, though. He needed to convince the undecideds and fence-sitters that he's fit to serve 4 more years, and last night would have put them off. Does that mean that some will vote for Trump instead? Some. Some may decide to stay home. Some may decide to vote 3rd party.
I watched with one of my brothers who is not unwilling to consider Trump. He didn't think either candidate was very good. (We were both rolling our eyes when it devolved into comparing their pars in golf. Any questions that they're both too old for the job?!) My other brother listened on the radio. He said this: "I thought Biden sounded reasonable (though old) while Trump was his usual lying crazy self. I think Biden's a good President but he's not very good at playing the part of the President on TV." Just an interesting point, I thought, especially as he listened to what they said, without watching how they looked.
I'm going to ruminate a bit over what the Dems should do, but I'm pretty angry at the party. They could have taken Biden at his word, that he'd be a one-term president, and have groomed a successor. They could have at least swapped out the unpopular Kamala Harris as running mate. Yes, these are not usual choices, but neither are these usual times. Trump threw decorum and old-school political norms out the window a long time ago. They should know that by now.
Biden had a much better day today. But does that mean that, at his age, he's more prone to good days and bad days? That's a concern. I absolutely agree with you that Biden and his team would make better stewards on the domestic and international stage than Trump and MAGA, for the next 4 years, but I'm not the one they have to convince. I really do wonder if the Dems will regroup and pose other options by the convention. That's the deadline. The next scheduled debate is after the convention. That's too late to regain voter confidence, and, frankly, if I were Trump, I'd refuse to debate Biden again. He can only lose ground.