Thanks for that input on the evidence and witness selection process. I have to agree that you are very likely correct that Harris or Leahy or any other Dem Senator cannot be sworn in as both judge and jury.
But doing so would seem to provide a scenario where Leahy (for example) as Judge rejects some evidence favorable to Trump, the Republicans object, a vote is held and, at least theoretically, it could a 50R - 49D vote and that would reverse the Leahy decision,.
Since Romney and a few other Trump hating Republican Senators can and probably will vote with the Dems the 50-49 outcome is admittedly unlikely. But would the Dems take the risk of naming a sitting Dem Senator as the Presiding Officer of the trial. I’m not so sure they would. An ex-Senator would seem to be a better choice for the Dummies.
I don't think that's possible.
There are strict rules about who is allowed on the Senate floor, and whether those allowed are allowed to speak.
Normal Senate rules would apply. The President of the Senate would preside. If the President of the Senate is not there, the President Pro Tempore presides. If the President Pro Tempore is not available, a designated Senator presides over the day's proceedings. That's why you always see different people at the gavel on different days.
So, one way or another, without Harris presiding there must be a Democrat Senator who steps up, because no Republican would agree to do it -- not even Romney, I suspect, unless he is signaling his intent to switch parties by doing so. If he did, he would be finished as a Senator from Utah.
-PJ