A person who is not the President can not be Impeached. “No Person except a natural born Citizen... shall be eligible to the Office of President”, if a person is ineligible they are not President.
No disagreement from me there, Ray. However, neither of us is cashing a SCOTUS paycheck at the moment, nor a CASC ducat either.
This is the cognitive dissonance that's going to fracture the country. He is, but he ain't.
The 12th Amendment says that whoever receives a majority of the votes of the Electors “shall be the President.”
Obviously determining eligibility must be accomplished before or at the early January Joint Session of Congress that is held to count and certify the votes of the Electors.