Former president Donald Trump’s legal team will make its case Friday in his impeachment trial. And it’s likely to be heavy on the idea that the proceedings themselves are unconstitutional. The vast majority of Senate Republicans have voted that you can’t try a former president. And several have indicated that, regardless of Trump’s culpability for inciting the Jan. 6 Capitol riot, they’ll vote to acquit on that narrower, procedural question.

But a new letter from hundreds of legal scholars, including several prominent conservative ones, argues that GOP senators now have a duty to evaluate the actual evidence. Because the Senate voted that it has jurisdiction, they argue, senators’ oath of office requires that they decide the case on the merits — i.e. Trump’s actions.

“The former President chose to raise a jurisdictional argument in a motion to dismiss the trial,” states the letter, which was shared with The Washington Post. “This body, exercising its considered judgment, determined that the Senate does have jurisdiction to try this case and so resolved the issue. … Now that the Senate, as a collegial body, has ruled on the jurisdictional question, individual Senators should respect and honor that determination of the Senate as a body, even if they might have disagreed with it as an initial matter.”

The letter follows previous ones from many of the same experts dismissing the argument that the trial is unconstitutional and rebuking another of the Trump team’s chief claims: that his speech was protected by the First Amendment.

The new letter’s signatories include Charles Fried, the former U.S. solicitor general under President Ronald Reagan whose name has come up repeatedly this week; Stu Gerson, a top Justice Department official under George H.W. Bush; Paul Rosenzweig, a top Homeland Security Department aide under George W. Bush; and Peter Keisler, a former acting attorney general in the latter Bush administration.

Lead House impeachment manager Jamie Raskin (D-Md.) made a similar argument Thursday.

“It has already been decided by the Senate on Tuesday that the Senate has constitutional jurisdiction over this impeachment case brought to you by the United States House of Representatives,” Raskin said. “So, we have put that jurisdictional constitutional issue to bed. It is over. It’s already been voted on. This is a trial on the facts of what happened.”

Republicans, though — including some who have been accused of not paying attention — have stuck by the argument.

“You’re not going to get anything but condemnation from me for what happened with those criminals at the Capitol on Jan. 6, but that doesn’t make the trial any more legitimate than it is, which is totally illegitimate — no basis in the Constitution,” said Sen. Josh Hawley (R-Mo.). Republicans including Sens. Marco Rubio (R-Fla.) and Mike Rounds (R-S.D.) have made similar arguments.

The letter cites senators’ oaths to “defend the Constitution of the United States against all enemies, foreign and domestic,” and to do “impartial justice according to the Constitution and law.”

“Having considered and properly resolved that question, you now have a duty — from your two oaths — to weigh the evidence before you,” the letter states. “You should not rely solely on a procedural argument that has already been voted down by this body, and certainly not on legal sophistry.”

It concludes: “It is now your turn to honor your oath as you weigh the evidence and arguments presented, even though it may require you to put our Constitution and the rule of law ahead of your own political allegiances. The eyes of the entire nation and future generations are upon you. Will you stand true to your oath?”