"As the story goes, Godel was preparing for his US citizenship examination in 1947 when he claimed to have found a 'loophole' in the constitution that allowed the US to elect a dictator." Crazy Donald's current coup attempt* makes it clear that Godel was right to be concerned.
It must be possible to prosecute a sitting president.
* Al Gore is the one who had the US presidency stolen from him, not crazy Donald. (Setting us back twenty years in trying to deal with climate change.)