I first met Bobby Kennedy Jr. when he showed up one summer afternoon in 1976 at the door of my ordinary suburban home in the company of a friend from Harvard named Peter Shapiro, who was running for a seat in the New Jersey State Assembly. I was 9 years old, and not particularly thrilled about our family’s recent move from Brooklyn to a street of empty suburban lawns whose nearest point of interest was a candy store a mile or so down a steep hill. The two polite, handsome young men in navy blazers, both in their 20s and...