Nelson Rising, chairman of Tom Bradley’s 1982 campaign for California governor, still remembers the phone call. Bradley called him shortly after 4 a.m. on a long Election Night, when it was clear Bradley had lost to Republican George Deukmejian. “You were right,” Bradley told Rising a bit wearily. With those words, Bradley, the Democratic mayor of Los Angeles, acknowledged that a political mistake had cost him the governorship. And, despite all the theories that the election produced a “Bradley effect” that could hurt black candidates such as Bradley — and, a quarter-century later, Democratic presidential nominee Barack Obama — the...