U.S. Republican presidential candidate front-runner Mitt Romney is watching his lead slip in polls in South Carolina ahead of the states primary election on Saturday.

Trailing closely behind Romney is key rival, Newt Gingrich, who recently won the endorsement of Texas Governor Rick Perry after the governor withdrew from the race.

Moreover, recent news that former Pennsylvania Senator Rick Santorum actually bested Romney in the Iowa caucus following a vote recount has dealt another blow to the front-runner.

Observers say Romney, who won the New Hampshire primary last week, will suffer a serious setback if he loses in South Carolina this weekend.