Only in recent days have questions emerged about his stand on abortion, his votes in Congress, and his endorsements of Romney over John McCain in 2008, and Senator Arlen Specter over Pat Toomey in 2004.

If rival candidates decide to go negative on Santorum - as they have on Newt Gingrich and Ron Paul -- they have plenty of material with which to work.

Santorum is beloved among "values voters" for his stand on abortion, gay marriage and other social issues. But his record is rich in polarizing policy positions and questionable associations that support the charge of "Washington insider."

For example, his million-dollar-plus 2010 income included payments from a lobbying firm, an energy company engaged in controversial "hydrofracking" and a hospital conglomerate that was sued for allegedly defrauding the federal government.