no doubt team trump has done an amazing job at normalizing horrendous behavior to the point where it doesn't stand out (and thus, offend) as much. pick any one terrible thing he's said or done in the past year and make believe it was said or done by Obama or Clinton...the country would be outraged and they'd be on their way out the door.
his re-election could hinge is whether all the moderate republicans/independents/democrats who hated hillary and held their noses and voted for him will be as motivated to come out in 2020 and do it again. trump's base is sizable but still barely 40%, all those nose-holders are the ones who put him over. when all those moderates in Wisconsin, Michigan, Ohio, Pennsylvania, etc. don't see all their manufacturing jobs return, when all the college-educated suburban women think about how disgusted they are by his personal behavior, and when lots of trump-supporting midwestern farmers declare bankruptcy due to his tariffs, they might feel burned. not that they'll suddenly vote for the democrat, but they're much more likely to just stay home on Election Day. once bitten, twice shy.
of course, it also depends hugely on who the democrats have up against him, obviously.