The big question — at least to us — after the first day of the trial of President Trump is what Senator Schumer is talking about when he says the Democrats will present “new” evidence. The majority leader made the comment Tuesday at a news conference. “I believe the managers will present a very strong case,” he said. “The evidence will be powerful. The evidence, some of it will be new.”

What makes that a point to mark is that in a regular criminal trial, the prosecution isn’t allowed to spring new evidence on the defense in the middle of the proceedings. Due process requires that all evidence be presented to the defense beforehand. The idea seems to be to afford the accused with the greatest chance of defending himself. Then again, too, the Democrats want no part of due process.

That has been evident from the start of this impeachment, which was rushed through the House with no proper hearings or adversarial process. Indeed, it’s been evident from the start of President Trump’s first term, when the calls for his impeachment began welling up from the Democrats. The defense Tuesday showed video of one Democrat after another calling for impeachment — in some cases, years ago.

The Times news story mocked that video. It asserted that the compilation was a “false equivalency” — because “none of those comments led to violence” the way the Democrats’ video suggested President Trump’s words led to the violence. By our lights, what the defense lawyers intended was simply to show that the Democrats have been intent on impeachment from the start of Mr. Trump’s term.

The main question the first day, though, was whether the Senate has the authority to try Mr. Trump after he’s out of office. Our opinion — a minority view, we understand — is that it was a bracing good argument from top to bottom. Even if the most salient point went unmentioned — namely, that, had the Senate been willing to bestir itself, it could have tried Mr. Trump while he was still in office.

That, of course, would have violated Senate Rule 1a (“avoid dispatch”) and Rule 1b (“eschew effort”). The solons didn’t even acknowledge the long gusts of flattery of the senators’ own wisdom that issued from the lead defense lawyer, Bruce Castor. When he started complimenting the prosecution lawyers, we’re told by the Times, Mr. Trump, watching from Mar-a-Lago, finally blew his stack.

One of the points the defense made is that none of the many charges laid against the alleged insurrectionists included a count of conspiracy with the president. One would think, the defense seemed to be suggesting , that were the prosecutors in possession of any such evidence, they would have levied it. And, we’d add, again, would have been required to share it with the defense. It’s just part of due process.

Which brings us back to Mr. Schumer’s promise of “new” evidence. Nearly every newspaper is predicting that the Senate is going to determine that the President is in fact not guilty of insurrection. That strikes us as a reasonable prediction if the prosecution is merely going to juxtapose the President’s words with pictures of the violence, while leaving out his injunction to march “peacefully.”

We keep thinking, though, of Senator Dianne Feinstein’s attempt, at the last minute, to sandbag the confirmation hearing of Justice Kavanaugh. And, for that matter, the Democrats’ last minute attack on Justice Thomas at his confirmation. This may be a different kind of hearing. If, though, the House springs at the last minute “new” evidence that the president conspired in and intended the violence, the trial could take a different turn.