Texas Gov. Rick Perry is questioning former Pennsylvania Sen. Rick Santorum's conservative credentials.

Perry said Thursday that he's sometimes confused when Santorum talks about fiscal conservatism. Perry says the former senator loaded up federal legislation with so-called pork-barrel spending for his home state and calls Santorum a "prolific earmarker."

In the race for the GOP presidential nomination, Perry is casting himself as an economic and social conservative best suited to take on President Barack Obama. Perry has slipped in recent polling as Santorum, who also casts himself as the only true conservative, has risen.

Looking to halt Santorum's rise, Perry said, quote: "I love Iowa pork but I hate Washington pork."