COLUMBIA, S.C. (TheStreet) -- Republican presidential candidate Newt Gingrich has opened a commanding lead over rival Mitt Romney in South Carolina, according to a poll released Saturday.

According to the latest poll from the American Research Group, the former House speaker is leading Romney, 40% to 26%.

Newt Gingrich

Rep. Ron Paul of Texas was third, with 18%, while former U.S. Sen. Rick Santorum was fourth, with 13%, according to the poll.

The telephone poll of 600 likely Republican primary voters living in South Carolina was conducted Thursday and Friday. It has a margin of error of 4 percentage points.

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Gingrich has gained 7 percentage points and Romney has lost 6 percentage points since a similar poll conducted Tuesday and Wednesday, the American Research Group said.

The outcome of the South Carolina primary is being watched closely, because the contest's winner has gone on to win the Republican presidential nomination in every election since 1980, The Associated Press noted.

This article was written by a staff member of TheStreet.