To be fair, the summer Covid spike was likely an unusually bad period for Trump and the Republicans in Florida. It was never +13 though.
If Wisconsin results tell us anything, I'm not sure if COVID spikes actually helped Biden. He was improving in the polls, but that might have meant that Democrats were more willing to stay inside and respond to pollsters.
I posted a thread about this recently, the polls did have a late shift to Biden in Wisconsin which was unusual. So maybe the Covid spike cost Trump Wisconsin.
Marquette did not
If the average changed, presumably some trend occurred (the +17% poll wasn't even in the final average), and you shouldn't base your analysis on just one poll.
