Rep. Ron Paul of Texas, who is making his third run for the White House, has doubled his support, from 6% to 12%. Texas Gov. Rick Perry, who may be making a last stand in South Carolina, has the backing of 5% of likely primary voters, down three points from last month. Perry had a disappointing fifth-place finish in the caucuses.

Former Utah Gov. and former ambassador to China Jon Huntsman, who is campaigning almost exclusively in New Hampshire, is at 1%. The poll also indicates that 4% of likely GOP primary voters are unsure of who they’re backing.

So what’s behind Romney’s surge in South Carolina?

“As in New Hampshire, Romney benefits from an open primary,” says CNN Polling Director Keating Holland.