I think folks are mistaken when they think "being Presidential" is a big tide turner. People vote their reality.
I think there are definitely a good deal of folks out there who have tired of Trump's shtick. Tired of the endless drama and confrontations, Tired of the denials of science, truth. Tired of media bashing and conspiracy hugging.
Folks that yearn for smooth sailing. Folks who want to cancel the reality Presidency, just tired of Trump.
And katrinavirus just underscores the incompetence that has been on display but wans;t significantly harmful before.
Centrists, huh? Come for the money, stay for the racism.
One couple I talked to in an airport while our flight was delayed and gates changed were from NC and were early 60's. Very nice people who made a bad choice. They regretted that Trump was constantly acting like a jerk. Not racist, the guy even helped an Iranian woman find her gate, when she barely spoke English and had little clue where she should be. He was gone about 10 minutes helping the woman (I found it strange that a middle-aged Iranian woman would be traveling by herself with very little English).
And this was 2.5 years ago in the early days of Trump.
I really think the Trump barrage of nonsense and dysfunction has turned off a swath of independent/moderate voters. That's what Biden is counting on.