I was happy to find an article that answered my question: “Don’t the Republican senators have to at least pretend to be ready to make an impartial judgement in the impeachment case?” And I’ve learned from Prof. Jeffrey K. Tulis that they do. Like members of a jury they must take an oath and declare “I solemnly swear [or affirm] that in all things appertaining to the trial of the impeachment of [the person being impeached], now pending, I will do impartial justice according to the Constitution and laws. So help me God.” Now I don’t see how Lindsey Graham and Mitch McConnell, just to cite two, can possibly take this oath in good conscience and in compliance with the law. Mr. Graham, an intimate of the President, has already boasted “I’m not trying to pretend to be a fair juror,” and Mr. McConnell has pledged to work closely with the accused, that is with Trump’s, legal team. So we will have a trial with at least one potential juror announcing his verdict in advance and another collaborating with the lawyers of the person on trial. In an ordinary trial the prejudiced can be rejected from the jury at the voir dire. So we must rely on prejudiced senators to reject themselves. I propose that any senator who cannot truthfully take the oath should recuse him/herself from the impeachment trial. If they do not, I propose that there be an investigation into their words and actions during the trial, and if they have broken their oaths they should be charged with perjury.