You are accepting a convenient Republican argument, expressed by Sessions' Department of Justice, that a sitting president cannot be indicted.
Far as I know, the Supreme Court hasn't ruled against it.
I don't suppose anyone would argue that if the president murdered his wife on the White House lawn, he would not be indicted. So we likely know that theoretically, a sitting president may be indicted.
In my view, it's more a question of the nature of the crime. Does stealing an election, and thus winning it and becoming president on false premises, rise to the level of an indictment? I'd say so.