But in other ways the Democrats are lucky to have Trump to run against, as they were lucky in 2016. In a year when the fundamentals mildly favored Republicans, Hillary Clinton got to face off against the most-disliked G.O.P. nominee of modern times. And she would have beaten him — even with Russia, even with Comey — had her campaign taken just a few more steps to counter his team’s long-shot strategy to flip the Midwest…

As with 2016, so with politics since. Liberal hand-wringing about their structural disadvantages ignores the advantages that Trump keeps giving them — the fact that in the best economy in 20 years he can’t stop making people hate him, can’t stop missing opportunities to expand his base, can’t stop forcing vulnerable Republicans to kiss his ring and thereby weaken their own prospects.

Impeachment has only extended this pattern, with Republicans voting to shorten the trial even when it makes them look like lackeys, and too cowed in many cases to even take the acquit-but-still-condemn approach that Democrats took with Bill Clinton. So now most of the country thinks the president did something wrong, most of the country thinks Republicans are protecting him, and most of the country is open, entirely open, to voting Trump and the most vulnerable Republican senators out in nine short months.