Tell that to George Wallace. You did know Arthur Bremmer is OUT OF JAIL NOW!
Secret Service has a list of about 400,000 people to watch who have threatened to kill Presidents, VPs, Senators, Congresscritters, etc.
I'd say the odds are good enough that most candidates for most of the top level federal and state jobs in this country should be protected by guards.
I remember what happened in 1972. Again, it’s not that common. The average citizen in D.C. is under more of a threat than a candidate at a street gaggle on Capitol Hill. We should all have guards.