Mitt Romney was the inevitable nominee — until he wasn't. In order to sustain a lead, a candidate's message must resonate with the heart and the mind. Mr. Romney's cakewalk to the nomination has been stymied by the inability to get anyone excited about his campaign. He has supporters but not believers. Rick Santorum's message resonates with voters' hearts and minds (this week at least), because he is a true believer. He believes in his message, and his message is consistent with core Republican values. What gave Mr. Santorum the edge in Iowa, Minnesota, Colorado and Missouri can give him...