The major problem — one of the major problems, for there are several — one of the many major problems with governing people is that of whom you get to do it; or rather of who manages to get people to let them do it to them.
To summarise: it is a well-known fact that those people who most want to rule people are, ipso facto, those least suited to do it. To summarise the summary: anyone who is capable of getting themselves made President should on no account be allowed to do the job.
To summarise the summary of the summary: people are a problem.
N.B. I had always thought this was a truism (albeit slightly tongue-in-cheek), which went hand in hand with “quis custodiet ipsos custodes?”.