Rick Santorum has criticized Ron Paul for airing robocalls in Iowa claiming Santorum supports abortion rights and opposes gun rights.

“Ron Paul is disgusting,” Santorum told a handful of Fox News reporters on Tuesday morning, just hours before the start of the Iowa caucuses.

(Related: Mitt Romney “dissed” Evangelicals; Rick Santorum to win in Iowa, Bob Vander Plaats says.)

Paul on Monday called Santorum “very liberal.”

“Have you looked at his record? Go look at his record. He spends too much money. He wasn't leading the charge to slash the budgets and vote against big government,” Paul is quoted as saying by The State Column.

The verbal sparring comes as the GOP rivals fight for a second place ticket out of Iowa.

Meanwhile, The Fix, a blog of The Washington Post, quoted Paul campaign chairman Jesse Benton as saying that “it sounds like Rick Santorum can't take the heat and is wilting under scrutiny.”

(Related: Ron Paul reiterates claim that an AIDS patient is “a victim of his own lifestyle.”)