Rick Perry is the first one of his rivals to single out Rick Santorum in a new radio ad which will run in Iowa starting today. Santorum has risen to third place in some opinion Iowa opinion polls of likely caucus goers.

Earlier this morning at an event in Washington, Iowa, Perry attacked Santorum for being a " prolific earmarker" during his career in Congress. The radio ad continues that line of attack, drawing attention to Santorum's support for such controversial projects as the Alaska "Bridge to Nowhere."

The two men are vying for support from the robust conservative evangelical community in Iowa. Perry, once a frontrunner in the race, has flagged in polls, while Santorum has only recently seen growing support after spending much of the last year in Iowa.