I don't think Trump is going to fu it up that badly. He'd have to screw a hooker and get caught on video, say something worse than there's a lot of good people here, or Hitler had some good points, to screw this up bad enough to lose.
By the way, Trump showed a lot more reserve than he has shown in office or in any of his campaigns, at the debate. It's not much of a bar to clear. He kept his barbs fairly reserved and limited in # for himself. There would have been a lot more nasty barbs coming out of his mouth in the past. He would have constantly pushed the time limits, and tried to speak over Biden before. I only saw him do this a couple of times, and it was over in 5 sec or less. He barely made fun of his mental problems, maybe once that I can recall. He would have used nicknames much more prevalently. He intimately called him Joe(not sleepy joe) Trump let a lot of points go, that Biden laid open for Trump to get nasty over. Trump was no angel, he just was in comparison to past performances. He waited till they got into it over their golf handicap, and at the right moment said 'Let's not act like children.' They were both acting like children, but he said it at the right moment to make himself look better.
If Trump had followed these kinds of advice in 2020, he might have still been in office, god forbid.