From the start, Mitt Romney's search for a running mate was a kind of ghost story, a process haunted by the specter of a certain former governor of Alaska. After their searing experience with Sarah Palin four years ago, Republicans vowed their next vice-presidential nominee would be someone serious and substantive.
In naming Wisconsin Representative Paul Ryan as his running mate on Aug. 11, Romney chose someone as deep as Palin was shallow, a studious wonk known for his mastery of that most substantive of all issues: the federal budget. Running mates are often chosen for their credentials or because of...