For today’s G.O.P. is, fully and finally, the party of Ronald Reagan — not Reagan the pragmatic politician, who could and did strike deals with Democrats, but Reagan the antigovernment fanatic, who warned that Medicare would destroy American freedom. It’s a party that sees modest efforts to improve Americans’ economic and health security not merely as unwise, but as monstrous. It’s a party in which paranoid fantasies about the other side — Obama is a socialist, Democrats have totalitarian ambitions — are mainstream. And, as a result, it’s a party that fundamentally doesn’t accept anyone else’s right to govern.