The first debate and then immediately catching COVID. If he had actually taken the time to prepare for the debate and pulled off a clear win against Biden - even while still being Trump - and then capitalized on that positive media attention to do... anything, he might have gotten the game changer he needed.
Yeah the first debate where he incredibly missed an open goal against an awful Biden seemed like it was his last chance. After that the Covid hospitalisation sucked the oxygen out of the rest of the campaign.
