The bottom line is that there is no clear answer. This issue has been the subject of dispute since the very first impeachment in 1797. Then, the Senate voted 14-11 to dismiss the articles of impeachment of Senator William Blount for lack of jurisdiction, although it was not clear whether this was because Blount had already been expelled from the Senate or because Senators are not officers subject to impeachment in the first place.
The Senate has claimed jurisdiction to try former officers more than once, and actually did try one, William Belknap, in 1876. Belknap was acquitted, and no other former officer has ever been convicted or, I believe, even tried to a verdict. The Senate’s jurisdiction to do so has usually been challenged, but not in court: with no convictions, no one has had standing or a reason to challenge the Senate’s jurisdiction in court.
So the answer to your question is in dispute. And it probably will not be resolved this time, because I doubt there are enough votes in the Senate to convict.
Thanks for your well-reasoned feedback. Agreed.
This seems to be a dangerous tactic for the deep staters. Obviously, they could care less about whether or not it’s constitutional as they only mention it when it suits their purpose. The danger, I would think, would be found in Trumps defensive tactics. An impeachment trial would be widely covered live by all networks. If Trump was able to bring all this evidence of voter fraud they claim to have, and the left’s propaganda apparatus is not able to suppress and obfuscate, the American people might get to see what really went on in the run up to, the election itself, and the after hours operation. Of course, John Roberts could rule none of it inadmissible if that’s what his masters command.