In murder mysteries, it’s a cliché to say “the butler did it.” In the real history of U.S. political assassinations and assassination attempts, there’s a corollary: “the lunatic did it.” Except that it’s really more of a truism than a cliché. Look at the list of people who have killed or tried to kill presidents. It’s full of nutjobs: Richard Lawrence (almost killed Jackson), Charles Guiteau (killed Garfield), Leon Czolgosz (killed McKinley), John Hinckley (almost killed Reagan), etc. There are exceptions. John Wilkes Booth would not have qualified for an insanity defense. But when a gunman targets a politician, lunacy is probably one of the first motives to consider, just as detectives are wise to investigate husbands whose wives die in strange accidents. It’s amazing how eagerly some people jump to different conclusions.