While Democrats duel, the unofficial Republican nominee considers a vice president. John McCain should start by asking what he needs. The admiral’s son fits two legs of his own party’s three-legged stool: foreign policy (zinging terrorism) and economic (scoring spending). Alas, he is out to sea with social and cultural conservatives, the one group without which national Republicans once routinely lost, and will surely lose again. According to a new Pew Research Forum poll, 44 percent of the electorate terms itself “born-again.” Politically, these Christian, mostly Protestant, evangelicals are the Republican Party’s largest block: 35 percent of George W. Bush’s...