How impeachment complicates the Democratic primary

For one thing, if the Senate held a trial and voted to acquit, then a good portion of the public would see the issue as having been dealt with. Not partisan Democrats, of course — but those folks are going to turn out to vote anyway. Infrequent, unaffiliated, and swing voters might be more likely to interpret the result as evidence that both sides view the matter through partisan lenses and tune it out. And the Democrats likely can’t win the electoral college — or the Senate — without those voters.

You might think that if the GOP played blatant partisan defense for the president, that would agitate the Democratic base to a greater degree and give them an electoral edge. But that’s not how the Kavanaugh fight played out. The Democrats lost that one, but the Republicans remained supremely mobilized even after victory — and that’s what gave the GOP the boost they needed in the Senate. If Susan Collins, Joni Ernst, Cory Gardner, Martha McSally, and Thom Tillis all hold the line in a Senate trial, then they must believe they have more to fear from crossing the boss than they do from crossing anti-Trump voters in their states. That should give Democrats pause before assuming impeachment will be enough to flip those seats.

Then, while the inquiry is ongoing, there’s a real possibility that the allegations move in the minds of at least some of the public from the political column to the criminal one. The standards of evidence could move from “do I want to hire this guy again?” to “is he guilty enough to convict?” — and attacks could feel more like prejudging the case than weighing it and finding the president wanting.