In this scenario it’s hard to imagine that Trump’s approval ratings wouldn’t have floated up into the high 40s; they float up into the mid-40s as it is whenever he manages to shut up. All the structural impediments to a Democratic recovery would loom much larger, Trump’s re-election would be more likely than not, and his opposition would be stuck waiting for a recession to have any chance of coming back.
Then consider a second counterfactual. Imagine that instead of just containing himself and behaving like a generic Republican, Trump had actually followed through on the populism that he promised in 2016, dragging his party toward the economic center and ditching the GOP’s most unpopular ideas. Imagine that he followed through on Steve Bannon’s boasts about a big infrastructure bill instead of trying for Obamacare repeal; imagine that he listened to Marco Rubio and his daughter and tilted his tax cut more toward middle-class families; imagine that he spent more time bullying Silicon Valley into inshoring factory jobs than whining about Fake News; imagine that he made lower Medicare drug prices a signature issue rather than a last-minute pre-election gambit.
This strategy would have given Trump a chance to expand his support among minorities while holding working-class whites, and to claim the kind of decisive power that many nationalist leaders around the world enjoy. It would have threatened liberalism not just with more years out of power, but outright irrelevance under long-term right-of-center rule.
But instead all the Trumpy things that keep the commentariat in a lather and liberals in despair — the Twitter authoritarianism and white-identity appeals, the chaos and lying and Hannity-and-friends paranoid style — have also kept the Democrats completely in the game.