The populist hero was born on a small farm not far from the Canadian border. As a boy, he scraped together money by raising chickens and managing a grocery store. He then worked his way through an unprestigious law school, and enlisted in the Marines to fight for his country.

Nearly every four years, millions of Americans who belong to that minority that cares about politics fall in love with an insurgent candidate for president. In 1964, conservatives swooned over Barry M. Goldwater; four years later, anti-war liberals rallied to Eugene McCarthy or Robert F. Kennedy. More recently, Patrick...