Yeah even in 2016 when I thought Hillary would win, I was very worried that a "Smart Trump" would swoop in in 2020 and demolish her and then we'd *REALLY* be in trouble. This year's midterms would have been a disaster for us too in this scenario so who knows what congress looks like at that point.
I'm cheerful.
Both are likely true, although I feel like incumbency advantage and GOP overreach would've helped Clinton's re-election. You *know* she would've been impeached by now, and that didn't play too well for the GOP the last time they tried to impeach a Clinton.
But 2018 would've been an unholy disaster. Lose the Dem senators in all the Trump states plus Minnesota and Virginia. Lose some of the few Dem governors remaining aside from Illinois which would've flipped back (New Jersey also reverting the previous year, but Virginia is lost), but Pennsylvania and Minnesota go full-tilt-red.
Only the House would be okay if only because the GOP is nearly maxed out there anyway. GOP +10 in the House maybe.
Edit: as far as smart Trump goes, the issue is that every year that passes makes Trumpism less viable. Trump worked by taking advantage of the distribution of white rural voters for the electoral college in a manner similar to how the GOP is maxed out in the House, but this strategy could only work for so long. After 2020 some of those midwestern states will become less important in the electoral college, while the demographic shift in the Sunbelt continues and the reliable GOP sunbelt states become less reliable. Someone coming back with the same brand of racism, even disguised by kind words, would not find the audience in the places they would need to make a difference.