during the 2016 election, there was a lot of people that were turned off by Hillary for various reasons, especially political history. whereas trump was somebody new and not a career polititian, so a lot of people were willing to give him a chance, if nothing more than to just give him a shot.
well 4 years goes by and he's done a lot to make people dislike him, including poor policy decision, exacerbating racist ideologies, and failing to uphold campaign promises. While his supporters probably will still vote for him, i imagine that he's thouroughly quashed his chances with independents and centrists.
Now Biden isn't charismatic and a lot of peoples last choice on the ballot, but he is somebody who has had expertise in govenment, and is associated with Obama whom a lot of people liked or were at least tolerant of. So the prospect of moderates and centrists to view Biden as being a safer choice, and a return to normalcy after multiple years of unrest during the trump presidency is promising.
barring the possibility of voter suppression and intervention, i can see Biden winning on the backs of many moderates who have buyers remorse from voting for Trump. The issue is that trump is doing all he can to ensure his victory, so i expect more shenanigans from here on out
the problem for him is that he has no subtlety or tact in his tactics. people are constantly aware of what he is doing because he more or less tells people in advance, and even flaunts it. This works for his supporters cause it shows his devil may care attitude, but it allows other people to prepare and report on it. it makes people aware of how much is at stake, and how fragile their situation is. if trump was more subtle and smart about his tactics, i thouroughly believe he could have anything he wanted. but as it is, he is causing people that don't like him and those who fear him to prepare and be on guard.
i can see things going either way, with either a trump win or a biden win. If i had to put my money on anything, it would be Biden because moderate and independent voters have had their taste of trump, and probably seek stability