Of the things that separate Americans politically, the "God gap" may be the most powerful. Republicans enjoy a big advantage among voters who are religious and, if Democrats aren't careful, the Supreme Court confirmation battle over John Roberts could turn the gap into a chasm. Religion is already raising its head as the Senate preps for its September hearings on Roberts. A devout Catholic, he has been asked by at least two senators about the role his faith would play in judicial decisions. The answers have been confusing: According to one senator, Roberts said he would have no trouble following...