When President John Kennedy visited Dallas in November 1963, he was greeted by a full-page newspaper ad accusing him of being a communist fellow traveler. To his wife he observed, "Oh, you know, we're headed into nut country today." The city, according to historian William Manchester, was a "mecca" for "the Minutemen, the John Birch and Patrick Henry societies." In the hours following Kennedy's assassination, aides assumed a right-wing radical was responsible. When Robert Kennedy informed Jacq...