We are in a standoff over the Senate impeachment trial of President Trump, and something — or rather someone — has got to give.

House Speaker Nancy Pelosi (D-Calif.) says she needs assurances about witnesses before she’ll send the impeachment articles over to the GOP-controlled Senate, because she’s worried about McConnell holding a sham trial. But she’s also dealing with unrest among some Democrats, and she had to reassure them Thursday by saying she wouldn’t withhold the articles indefinitely and would probably send them over “soon.”

Senate Majority Leader Mitch McConnell (R-Ky.), meanwhile, has held firm to the idea that such determinations must wait until after the trial starts. And importantly, he appears to have unified Senate Republicans behind that idea, including would-be crossover votes such as Sens. Mitt Romney (Utah), Susan Collins (Maine) and Lisa Murkowski (Alaska).

McConnell’s argument is basically this: That’s how the Bill Clinton impeachment was handled 21 years ago, and those rules were approved unanimously. “All we are doing here is saying we are going to get started in exactly the same way 100 senators agreed to 20 years ago,” McConnell said. “What was good enough for President Clinton is good enough for President Trump.”

And that has proved a compelling argument to those GOP senators. “I’d like to hear from [former national security adviser] John Bolton and other witnesses to provide information. That process will accommodate that,” Romney said. “The Clinton process allows for a vote on witnesses to occur after opening arguments.”

But while it’s true that’s the process followed by the Clinton impeachment, there is one very important difference: In the Clinton case, the impeaching party in the House also had the majority in the Senate. That means their party had total control over the rules moving forward and didn’t need to negotiate anything ahead of time. In this case, once the articles are sent over, the impeaching party effectively cedes any control over what will come of the trial for the president they just impeached.

During the Clinton trial, the Senate unanimously passed a set of rules that allowed for votes to subpoena witnesses later on. It was noncontroversial because there really wasn’t any reason for such negotiations to take place on the front end. If Republicans wanted Monica Lewinsky, Vernon Jordan and Sidney Blumenthal to testify, they could just vote to do it later.

And that’s just what they did. Three weeks into the trial, the unanimity was gone, and the Senate by a party-line vote directed then-Supreme Court Chief Justice William Rehnquist to issue subpoenas for those three depositions. The process worked for the Republicans because they could essentially determine it all as they went. The GOP-majority House impeached Clinton and handed the matter over to a GOP-majority Senate.

But to pretend there was unanimity over the rules is to gloss over a whole lot of nuance. If the Democrats controlled the Senate back then and said there would be no witnesses or new evidence, as McConnell has suggested, would the package of rules have passed unanimously? Probably not, it stands to reason. But there was no way Democrats could stop Republicans from putting on a thorough trial of a Democratic president, so there wasn’t really any use in opposing the package of rules at the start.

The Democrats are similarly powerless today, and they’re dealing with a Senate leader who has made little secret of his desire not to hold a robust trial. They do have a slightly bigger minority, though. Back then, they had 45 votes and needed to pick off six Republicans to beat any subpoenas; today, they have 47 and need four. So if they try to subpoena Bolton, who has declared a willingness to testify, they’ll need to get the likes of Romney, Collins, Murkowski and one more GOP senator to vote with them.

That’s possible, but once the process starts, they basically have no leverage. Pelosi’s only card to play was to withhold the articles and hope it would lead to pressure on McConnell to come to the middle. Bolton’s declaration that he would testify and some new evidence might have supplied a little bit of pressure, but McConnell appears characteristically immovable. And as long as the Romneys and Collinses are with him, he has little incentive to budge. Pointing to the Clinton rules has provided a very plausible argument for those moderate/swing-vote GOP senators to sell as they toe the party line, even as it significantly decreases the odds of as thorough a trial as we had with Clinton.

And one wonders if McConnell would feel so tethered to precedent if the roles were reversed. Given his handling of the Merrick Garland nomination — and his later comments about how the GOP wouldn’t follow that precedent if there were a Supreme Court vacancy this year — I suspect we know the answer.

This post has been updated.