The temperature in the GOP pot must be rising. Cause some are starting to feel the heat.
I believe it would be best for all concerned to speak with Roberts ahead of time and have him open the impeachment, take a motion or point of order from a GOP Senator that calls into question if the Constitution allows for Impeachment of a US Citizen who is not an officer of the nation. The Roberts should rule that no, that is not constitutional and dismiss the case as being moot.
I doubt that will happen but hey it is a nice idea and would establish a precedent that would work to prevent impeachment of former Presidents, and others such as members of Congress.
Someone brought to my attention the possibility of using the 14th Amendment, Sections 3 and 5 as possible ways to impeach a non serving person to keep them out of office. I don’t have enough lawyerly skills to evaluate this.