Before opening arguments for the Senate trial for President Trump’s impeachment gets underway, senators took an oath of impartiality, administered by the chief justice of the United States:

Which raises the question: How can senators in good conscience take this solemn oath on Thursday when many of them have already decided whether the president is guilty or not?

The answer as I see it after studying the trial rules and talking to various constitutional scholars is this: In this setting, impartiality is subjective, and even if senators were to break their own version of the oath, there’s nothing holding them to it.

Nothing in the rules the Senate agreed to in the 1980s says the chief justice or anyone else can punish senators for not being impartial. They are not held to a gag rule like some jurors in high-profile criminal trials. They can go on cable news in between and offer their opinions. They can step out of the Senate Chamber and tell reporters what they think of the evidence.

That might sound cynical — that such an oath at such a major moment for our country is just words without some kind of enforcement. But at the crux of this is the fact that the Founders put the president’s fate during impeachment in the hands of a political body. And so, political it will be.

That is because, to many Republican senators, the price for being seen as disloyal to the president is higher than the price of being seen as disloyal to their oath of impartiality. The same goes in reverse for Democratic senators, especially the four also running for president.

“The kind of people who are too principled to behave this way rarely become powerful politicians in the first place. Or if they do, they may not stay there very long,” George Mason law professor Ilya Somin told me in a recent conversation about Congress relinquishing its war power to the president because it’s politically convenient. It’s a sentiment that I think applies in a Senate trial.

That’s why Senate Majority Leader Mitch McConnell (R-Ky.) has felt comfortable saying he will run this trial in “total coordination” with White House lawyers. And then he can say this on the eve of the trial about the oath: “We will pledge to rise above petty factionalism and do justice for our institutions, for our states, and for the nation.”

To McConnell, impartiality means defending the president from what he sees as a politically motivated impeachment. (Or, perhaps even more accurately, what his constituents who will decide his political fate this November see as a politically motivated impeachment.)

Some Republicans point out that during the Bill Clinton impeachment trial, now-Senate Minority Leader Charles E. Schumer (D-N.Y.) made a similar point when asked why he was so vociferously defending Clinton even though he was about to be a juror in his fate.

“The Founding Fathers, whose wisdom just knocks my socks off every day, it really does, set this process up to be in the Senate, not at the Supreme Court, not in some judicial body,” Schumer said at the time. “Every day, for instance, hundreds of people call us up and lobby us on one side and the other. You can’t do that with a juror. The standard is different. It’s supposed to be a little bit judicial and a little bit legislative-political.”

Senators see everything through a political lens, even their oath of impartiality. And judging by the fact that the Framers gave the Senate the responsibility of holding impeachment trials, they seemed relatively okay with that.