For many years, Caroline Kennedy appeared to have an immunity to politics, rare among her family. Why the reluctance? Wasn't the whole point of being a Kennedy to hold some kind of elected office and, anyway, what would happen to all those governorships, congressional seats and Capitol Hill lunch tables if the Kennedys gave up filling them? Caroline, the only surviving child of the late President John F Kennedy, was resolute. Uncomfortable in the public eye, and doubtful of her appetite for the rough and tumble, she preferred the arty, affluent world she could see from the windows of her...