Santorum calls on Romney to release tax returns

Add Rick Santorum to the list of Republicans calling for Mitt Romney to release his tax returns.

"I don't know why he hasn't released his tax returns. I think he should," Santorum said in an interview Monday on the Laura Ingraham radio show. The former Pennsylvania senator added that it was important especially for "someone with [an] enormity of wealth," like Romney.

"Well, let's see how he manages his own economy," Santorum said.

Sarah Palin and Newt Gingrich have also called on Romney to release his tax returns. And President Obama's campaign has criticized the former Massachusetts governor for not doing so. The "Barack Obama" Twitter account, on Dec. 30, asked: "Why won’t Mitt Romney release his tax returns?"

Romney maintains he's complied with legal obligations on disclosing his wealth, adding he might release his tax returns in the future. His net worth is estimated to be between $190 million and $250 million.

On Sunday, Gingrich said he planned to release his income tax return on Thursday. He also reiterated his call for Romney to release his tax return.

"If he plans to stay in the race, [he] ought to plan to release his records," Gingrich said on NBC's "Meet the Press."

Meanwhile, Santorum refused to accept the idea that Romney, who's generally led in the polls in both South Carolina's primary and nationally, would be the presumptive Republican nominee after the Palmetto State's primary on Jan. 21. Santorum said that was just the establishment media and politicians anointing Romney as the "crown prince."

"This is the establishment Republicans telling the people of South Carolina who they have to vote for," Santorum said on Monday.