As I write, the House impeachment managers are delivering the article of impeachment to the Senate, commencing the trial. And it seems Republicans have increasingly coalesced around the idea that this trial will be unconstitutional, basically because Trump is no longer president. There’s been some scholarly dispute whether or not you can still hold the trial after the defendant has left office. The text certainly seems to contemplate impeaching current officials. But, the argument goes, if you cannot impeach a former official then the ability to disqualify from holding further office would become a nullity, because any impeached official could just resign immediately before the vote to convict, mooting the whole trial. The historical precedents are a bit murky; they’ve held trials for officials who had already resigned, but never convicted a former official. The majority scholarly position is definitely that you can try a former official, as shown by this letter signed by dozens upon dozens of professors.
But never mind that. Let’s say we take these Republicans at their word that they think the trial is unconstitutional. What then? Well what’s going to happen is presumably that they will sit down, take their oaths as members of the court of impeachment, listen to the trial, and then vote to acquit. They will do so on the grounds that the whole thing was unlawful, which will let them evade actually taking a stand on whether what Trump did was impeachable. They want to do this, because they cannot actually bring themselves to say it was not, but also if they vote to convict his legion of rabid fans will tear them to pieces. And with their votes, Trump will be acquitted.
What should happen, though, is that they should boycott the entire thing. All of the actions described in the previous paragraph affirm the authority of the tribunal. If you actually believe that this trial is unconstitutional, you have a solemn duty not to participate in it. King Charles I understood this. After declaring the High Court that Parliament had established to try him for treason had no jurisdiction over him, Charles blatantly refused to participate in the trial. He entered no plea, he offered no defense, even though the predictable result was his conviction, condemnation, and beheading. That is in fact what you’re supposed to do when you think a tribunal like this is illegitimate!
But they won’t do that, because that would lead to Trump’s conviction by a two-thirds majority of those Senators who participate. They want to take their seats, and cast their votes, and bail him out, god knows why. And they’ll cling to the jurisdictional argument to excuse their own responsibility, as though an invalid court can have any more authority to enter a judgment of acquittal than one of conviction. (Literally what it means to lack jurisdiction is that you cannot pronounce judgment one way or the other!) And we’ll all have to pretend to take their argument seriously, even though they’re quite plainly not actually following its implications.