Republicans Rick Santorum and Mitt Romney are sparring over Santorum's support for his former Senate colleague, Arlen Specter of Pennsylvania.

Romney and Santorum traded barbs Wednesday night in a nationally televised debate in Arizona less than a week before that state's primary.

Santorum backed Specter in his 2004 GOP primary battle against a more conservative Republican, Pat Toomey. Specter narrowly defeated Toomey and went on to be re-elected that year. He switched parties and became a Democrat in 2008 but lost in the party's primary in 2010.

Romney says Santorum's support for Specter led to the passage of President Barack Obama's health care plan.

Santorum says he backed Specter because he promised to support President George W. Bush's conservative judicial nominees.