You are correct.
However...
There are some unique dynamics at play here.
With that said, Republicans should push for Leahy to preside, because they will then have a majority vote on the jury.
-PJ
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.