In one of the 2016 Presidential debates, Donald Trump made the assertion that if he were President, Hillary Clinton would be in jail due to the email scandal. Many strong supporters most likely believed this was possible, and perhaps even Trump himself believes the Presidency comes with omnipotent (read: dictatorial) powers to do whatever he wants. It does not work that way, however, as the President has only the power to appoint a special prosecutor to investigate certain actions, but not the power to prosecute people and throw them in jail at her or his own whim. Additionally, using this appointment power should be used with restraint, lest the public be concerned that the President's time and energy be wasted with appointing prosecutors simply to take revenge on people he or she doesn't particularly like.
Separately, criminal law does not seamlessly transfer into the political realm where people are "innocent until proven guilty," as pointed out by professors Vikram David Amar and Michael Schaps. Many Trump supporters responded to the women accusing Trump of sexually harassing them by stating that Trump cannot be viewed as guilty due to the "presumption of innocence" bestowed on all Americans. Yet Trump is not a defendant in a criminal trial as the professors point out; he is a candidate for President and the presumption of innocence not only does not apply in this scenario, it should be turned on its head. Candidates for President are and should be viewed under a microscope, with every character defect taken to be true unless and until it is proven otherwise. The candidate is being considered to run our country and a certain moral decency is expected and required such that any concern about their character should be considered when deciding who to vote for.