On October 10, 1963, U.S. Attorney General Robert F. Kennedy committed what is widely viewed as one of the most ignominious acts in modern American history: he authorized the Federal Bureau of Investigation to begin wiretapping the telephones of the Reverend Martin Luther King Jr. Kennedy believed that one of King's closest advisers was a top-level member of the American Communist Party, and that King had repeatedly misled Administration officials about his ongoing close ties with the man. Kennedy acted reluctantly, and his order remained secret until May of 1968, just a few weeks after King's assassination and a few days before Kennedy's own. But the FBI onslaught against King that followed Kennedy's authorization remains notorious, and the stains on the reputations of...