T he one trait shared by everyone who seeks the modern U.S. presidency is a sociopathic indifference to normal human behaviors and values. The demands, the ordeals, the strictures of the office; the expenses in terms of time, relationships, and health; the media scrutiny, the media stupidity; the unremitting company of Washington’s political metronome, ticking from hysteria to tedium and back again—theirs is a life that no stable, well-adjusted person would ever choose or desire. The only plausible explanation is that this species is afflicted by ambitions and grandiosities unfathomable to the rest of us.

Ponder, say, Newt Gingrich, who in 1992 wrote a memo announcing himself the “definer of civilization” and the “leader (possibly) of the civilizing forces.” Or the current President, who published a memoir at thirty-two years old, gave Queen Elizabeth II an iPod loaded with recordings of...