Last weekend, Harry Windsor and his wife, Meghan Markle, discovered a harsh truth about being a British royal: it’s an all-in proposition, with no scope for half measures or divided loyalties. Barely a week after the couple had proposed taking a “step back” from their official duties and spending most of their time in North America, the Queen rejected this idea and stripped them of their royal titles and entitlement to sup at the public purse.

After two days of legal arguments in the impeachment trial of Donald Trump, the Senate’s fifty-three Republicans are being reminded that membership in Trump’s party is a similarly all-embracing and restrictive proposition, but one that tars reputations rather than enhances them. At this stage, the only question is whether any of the fifty-three captives will do a Harry and Meghan and make a run for it. Sadly, it doesn’t look likely.

On Tuesday and early Wednesday morning, all of the Senate Republicans voted along party lines to block the House managers from subpoenaing more documents and calling additional witnesses, such as the former national-security adviser John Bolton and the acting White House chief of staff Mick Mulvaney. Then they settled in to listen to Adam Schiff and his colleagues lay out some of the voluminous evidence that Trump abused his office by trying to coerce the government of Ukraine into doing him a political favor. “It is clear from last night that we are now on a partisan, forced march towards a predetermined outcome,” Senator Sheldon Whitehouse, a Democrat of Rhode Island, commented on Wednesday, at a news conference with other Democratic senators.

Whitehouse was right, of course. In this drama devoid of suspense, the allotted role of the G.O.P. senators is to sit quietly and do whatever they are told by Mitch McConnell, the Senate Majority Leader, who informed us last month that he views the proceeding as a political one and himself as a virtual extension of the President’s legal team. “Everything I do during this, I’m coördinating with the White House counsel,” he told Sean Hannity, of Fox News, in December. At least some of the G.O.P. senators, especially those facing tough reëlection contests later this year, would presumably like some way to signal to voters in their states that they are seeking out all the evidence and taking it seriously, even if they don’t ultimately vote to impeach Trump. McConnell and the White House’s lawyers aren’t giving them that option.

Rather than stipulating to some of the established facts about the Ukraine squeeze play and arguing that Trump’s misdeeds don’t rise to the level of an impeachable offense, the President’s defenders are trying to curtail the trial to just a couple of weeks, rehashing Trump’s talking points, and making the bogus argument that impeachment requires specific violations of criminal statutes. “There was no quid pro quo for anything,” Michael Purpura, a White House lawyer, said on Tuesday. Jay Sekulow, one of Trump’s personal attorneys, alluded to discredited conspiracy theories about the Mueller investigation. Pat Cipollone, another White House lawyer, falsely claimed that Republican members of the House were barred from attending witness depositions.

Even some conservatives are crying foul. “Instead of sticking to the most defensible case for a Senate acquittal of Trump, Republicans from the president on down are making arguments that range from the implausible to the embarrassing,” National Review said in an editorial. The Republican lawyer George Conway, whose wife, Kellyanne, works for Trump, was even harsher about the President’s defense team. “They’re treating the American public, they’re treating the Senate, like they’re morons,” Conway said to CNN’s Jake Tapper. “It’s just outrageous.”

All this is ultimately Trump’s doing, of course. He never admits anything, demands total loyalty, and strikes out at anyone that transgresses these rules. As with the Windsors, you can’t be a half-in Trump Republican. Those who embark down that path tend to disappear from the political scene rapidly. Ask the former Republican senators Bob Corker and Jeff Flake. The banishment meted out to these dissidents was even more definitive than the one Buckingham Palace meted out to Harry and Meghan.

At a press conference on Wednesday in Davos, Switzerland, Trump suggested that he might prefer to hear from “a lot of people” at the trial, but that was just a head fake. His entire legal strategy is based on excluding any new evidence or testimony. During the same press conference, he gave the game away when he said, “Honestly, we have all the material. They don’t have the material.” He could just as easily have said: “The fix is in.”

Much has been made of the concessions that a group of Republican moderates, including Susan Collins, Lisa Murkowski, and Mitt Romney, elicited from McConnell on how the trial would be conducted. However, McConnell merely agreed that evidence collected in the House is admissible here and that both sides would have three days rather than two to present their cases. The only potentially significant climbdown came when he agreed to another vote on calling witnesses after the first stages of the trial have been completed.

But this concession will matter only if, between now and next week, at least four Republican senators summon the will to break with Trump on an issue he cares about more than anything—his own survival. “This is a moment, I think, of reckoning, not just for the country and for the rule of law and for the Constitution. It’s a very specific day of reckoning for the Republican senators who took this oath, and for the Republican Party generally,” Conway said in his CNN interview. “Are they going to stand for lies instead of truth? Are they going to stand for gaslighting instead of reality? Are they going to just do the bidding of this one man and put his interests over those of the country? That’s what this is about.”