Over the last 200 years, the country has elected a variety of colorful figures to national office. Drunkards, racists, slave holders, philanderers, war heroes, populists, demagogues, humanitarians, misogynists, embezzlers, patriots, and nepotists, all have walked the halls of the Capitol and the White House. Yet rarely has a man been sent to Washington who could be defined by all of those descriptors at once. Richard Mentor Johnson of Kentucky was one of those men. His heroic, controversial, and eccentric life made him notorious in his day, a tragic hero who walked the stage of American...