A year out of Harvard Law School in 1972, Sandy Berger was traveling with presidential candidate George McGovern as a speechwriter. When they landed in San Antonio for a rally, Berger caught a first glimpse of his future boss, bounding up the steps of the plane: a tall, striking young man, improbably clad in a Colonel Sanders white suit, who was serving as McGovern's Texas coordinator. Bill Clinton and Sandy Berger have been "real friends" ever since, says a senior Clinton aide. "You can see the affection when they're in the room together."
When Clinton weighed whether or not to run...