For politicians who are searching for an appropriate way to talk about their Christian faith in public, the Bible can sometimes appear to contain contradictory mandates. In Jesus’ Sermon on the Mount, he admonishes his disciples to pray in secret and “not be like the hypocrites, for they love to stand and pray in the synagogues and on the street corners to be seen by others.” Later, however, the resurrected Jesus, just before he is taken up to Heaven, implores his followers to go forth and “be my witnesses in Jerusalem, Judea, and Samaria, and to the ends of the...