Out of curiosity, what would be the right and legal way in the following situation:
Any US president suspects one of the presidential candidates to be involved in something illegal (maybe now or in the past) and goverments of another country might have serious information on this matter and could help.
What are the correct options?
a) Do nothing and wait until after the election so that the US citizen is not a presidential candidate anymore (risking that this person could then be actually the new president)?
b) Report/inform authorities: Which ones? FBI, CIA? Risking that someone in there then suspects the president/government to seek help from another country against a presidential candidate or trying to smear his campaign?
c) Possible illegal activities of US-citizens, especially presidential candidates, are not the presidents concern.