> And since they can’t indict him while in office..... <
As I understand it, that is only by custom. There really is no law that would prevent such a thing.
He can’t be prosecuted by the federal government while in office, because he’s in charge of the DOJ, so he would essentially be prosecuting himself. Hence the need for impeachment before prosecution, at the federal level.
At the state or local level, I think it’s an unsettled question. As far as I know, there is no law prohibiting it, but nobody has ever tried, so it surely would be challenged and probably have to go to the Supreme Court.