Rick Santorum's pitch to Republican voters is simple: He is the "true" and "consistent" conservative in the GOP's presidential nomination fight. He describes himself as "a candidate who, throughout [his] career, has not only checked the box on conservative issues but has fought for conservative issues." And he slams front-runner Mitt Romney for flip-flopping on abortion and the Wall Street bailouts and, most of all, for passing government-mandated health care reform in Massachusetts. If elected president, Santorum vows, he will end the "tyranny" of President Obama's Affordable Care Act. Yet as an up-and-coming congressman in the early 1990s, Santorum took...