Here are the three leading candidates for president in the Republican party, a party based in the South and in the interior, rural in nature, and backed in large part by social conservatives: the senior senator from Arizona, a congenital maverick with friends in the press and a habit of dissing the base of his party; the former governor of deep-blue Massachusetts, son of a Michigan governor, a Mormon who looks, sounds, and comes across as a city boy; and the former mayor of New York, the Big Apple itself, ethnic and Catholic, pro-choice and pro-gun control, married three times,...