Biden isn't really POTUS's opponent
His opponent is the coronavirus. He is flailing against a pandemic that is now surging as it hasn’t since late July, and especially so in regions (the South, the upper Midwest) considered his electoral strongholds. The Biden campaign has wisely never lost its focus on Trump’s cataclysmic failure to address the crisis. But even if it had, the morbid facts speak for themselves. The ever-replayed video of the White House gleefully playing host to a super-spreader event is our era’s Zapruder film. Trump wants to change the subject, but he can’t.
I would also argue POTUS is running against himself.