The other GOP hopefuls are focusing their attention along South Carolina's coast and attending church services and prayer breakfasts in the state, which has a large population of evangelicals and other conservative Christians.
Rick Santorum, Rick Perry and Newt Gingrich all say the fractured Republican field is boosting Romney's campaign, with social conservatives divided over an alternative candidate.
Yesterday, Santorum won the endorsement of an influential group of social conservatives and evangelical leaders in Texas. He tells "Fox News Sunday," once the field narrows to a two-person race, he'll "have an excellent opportunity to win."
Romney's rivals are pointing at his record at a private equity firm and his push for a health insurance mandate as Massachusetts governor as problems for this campaign.
Santorum says Romney's health care plan provided the basis for President Barack Obama's health care law, and "to give away that issue" would be "malpractice on the part of primary voters."
