An exclusive InsiderAdvantage poll released Sunday night shows GOP front-runner Mitt Romney gaining in his lead in the South Carolina primary, while former House Speaker Newt Gingrich is holding steady in second place.

In the poll of 720 likely registered voters in South Carolina GOP primary, Romney was leading with 32 percent of the vote. Gingrich was second with 21 percent, followed by Ron Paul with 14 percent.

The rundown:

• Romney: 32 percent
  
• Gingrich: 21 percent
• Paul: 14 percent
• Santorum: 13 percent
• Huntsman: 6 percent
• Perry: 5 percent
• Other: 2 percent
• Undecided/ No opinion: 7 percent

“The poll is among likely voters who are registered in South Carolina and are likely to vote in the Republican contest. The survey is weighted for age, race, and gender,” said InsiderAdvantage chief pollster Matt Towery.

“The only candidate to really gain any ground in this survey since our poll of last Wednesday night is Mitt Romney. Newt Gingrich is in second, basically even with where he was last week. Ron Paul is up by a point over our last poll, Rick Santorum is down by a point, but given the 3.8 percent margin of error, they basically are the same as last week.

“Huntsman and Perry are finding little traction,” Towery said of the poll results, compiled before news surfaced that Huntsman planned to drop from the race. “Basically, Romney has about a third of the vote from those who describe themselves as ‘Republican’ [these tend to be longtime traditional Republicans] and a third of those who, for whatever reason, describe themselves as ‘independent.’ He leads in the others in both categories.

"The other candidates divide up the other two-thirds of that vote . . . with Gingrich fairing the best among them among self-described ‘Republicans’ and Paul doing the best among those behind Romney among self-described ‘independents,'" Towery said.

The poll was conducted Sunday evening and has a margin error of 3.8 percent. It was weighted for age, race, and gender.