Democrats can't let go of Donald Trump even as a former president, so last week U.S. House managers walked their article of impeachment to the Senate for a trial. Their goal is to banish Trump from running for office again. The result may instead be his acquittal and political revival.

Democrats have already forced one impeachment trial, resulting in acquittal and no notable decline in his political standing. He lost the election due to his handling of COVID and its consequences. But now Democrats want to do it once more with feeling, after Trump urged his supporters to march on the Capitol on Jan. 6 with a goal of overturning the Electoral College vote for Joe Biden.

We've said Trump's actions — and failure to act to stop the riot as it unfolded — were an impeachable offense and urged him to resign. But now he is out of office and no longer the "imminent threat" that House Democrats said justified their rushed impeachment. The question is what good purpose a Senate trial will serve, and that isn't apparent.

The Democratic case is that Trump must be punished lest any future president try something similar in his final days. A conviction by two-thirds of the Senate would also open him to a majority vote barring Trump from running for public office again. But what if he is acquitted?

One problem is whether such a trial is even constitutional. The language in the Constitution refers to impeachment against a president while in office, and Trump is now a private citizen. Chief Justice John Roberts doesn't seem to believe he needs to preside over the trial because the Constitution stipulates that role for the chief only for a president. Senior Democrat Pat Leahy will preside instead.

In the only relevant precedent, the Senate held a trial of a former war secretary in 1876 after he was impeached and resigned. But senators acquitted William Belknap in part because some thought a trial after resignation was unconstitutional.

The evidence can support either view, but it's unsettled law and GOP senators are lining up to say it's unconstitutional. Perhaps the House managers will turn up evidence beyond what we already know that persuades the 17 GOP Senators necessary to convict. But most Democrats are already saying they need no new evidence since the facts of what Trump said and did are on the public record.

Meanwhile, Trump will be able to marshal a defense that he wasn't allowed to present in the House. He will have a new megaphone for that defense during the trial, and you can bet he will make the case that he is the victim of a sham, partisan show trial. He will mobilize his supporters to pressure GOP senators, who will have to make a hard political calculation.

It's easy for Democrats and the press to claim Republicans should vote to convict, but most want to run for re-election again. The rushed House vote — no hearings, no defense — also makes a vote to convict more difficult.