Pulitzer Prize-winning author Robert Caro has spent nearly four decades researching and writing about President Lyndon Johnson. His fourth book on the LBJ, "The Passage of Power," follows Johnson from 1958 to 1964. Lyndon Johnson was perhaps the most powerful majority leader of the senate. Yet he found himself virtually irrelevant as vice-president in the Kennedy administration. At perhaps his lowest point, a shot changed everything and Johnson immediately took the reins as the thirty sixth president. Caro calls it, without a doubt, Johnson's finest hour. Diane will talk to Caro about spending four decades researching and writing about the 36th U.S. President.