If you want the bad news all at once, the TL/DR is this:

(1) Trump can use normal tactics to win outright or make the race closer.

(2) COVID problems with election administration can take up to 6 percent off of Biden’s margin.

(3) Trump and the GOP might use historically unprecedented tactics to stay in power despite losing.

(4) pro-Trump foreign actors will be using similar but more aggressive tactics to their 2016 interference.