My biggest concern is that American voters overwhelmingly vote on how they see the economy going, and it's currently in the shitter.
You can give all the usual explanations, like "it's China's fault, Trump didn't shut down cities the governors did, nothing anyone could do", etc. But they don't matter; it's a question of how the electorate feels about the economy, and if it's negative it automatically goes against the incumbent.
I wish Trump had another 1-2 months to let the bounce back be fully felt. I still think he was planning for a "grand re-opening of America for business" style campaign at the Republican convention, but had to cancel, and thus lost his best pitch for re-election.
If everyone is still depressed about the economy by the end of October, the Rust Belt states are easily in play.