Rudy Giuliani could be the death knell of the Reagan Coalition, that successful alliance of economic, defense, and social conservatives forged in the 1976 Republican primary. In his insurgent campaign against President Gerald Ford, Ronald Reagan built the architecture for a durable political coalition of supply-siders, budget hawks, Cold Warriors, law-and-order advocates, welfare reformers, pro-lifers, defenders of the Second Amendment, and others. He integrated these main elements of the post-war conservative intellectual movement into a successful, winning political juggernaut that was, until recently, the Republican Party. In recent years the social component of the coalition has been augmented by pro-family...