COLUMBIA -Republicans are getting an early start in November's gubernatorial election in the Palmetto State with a large advertising buy in key markets.

Television viewers in the Charleston, Myrtle Beach, Columbia and Greenville markets can expect ads starting Monday, part of an early $200,000 Republican Governors Association ad buy, according to an official with knowledge of the purchases.

The campaign against Haley, from likely Democratic nominee Sen. Vincent Sheheen, D-Camden, is just underway. The Sheheen campaign declined to comment on the ad buy. Democrats say it's significant to see such a large advertising buy so early in the race.

"Nikki Haley's . deeply vulnerable and clearly the RGA knows it," said Kristin Sosanie, a state Democratic Party spokeswoman, in a statement. ". it's no wonder Nikki Haley had to desperately call in help from her buddies in DC. But no amount of interference from Washington will be able to make the people of South Carolina forget that Nikki Haley allowed their Social Security numbers to be stolen and then covered it up for weeks."

Sosanie was referring to the 2012 cyberattack on the state that compromised the tax returns of millions of businesses and people in South Carolina. A Haley campaign spokesman did not return a request for comment.

RGA spokeswoman Gail Gitcho declined to confirm the ad buy, but she did have an opinion on Sheheen.

"Vincent Sheheen's unyielding support for ObamaCare despite warnings of the damage it would cause in South Carolina proves that his support for liberal policies are out of step with the people of his state," Gitcho said in a statement.

"President Obama has plenty of politicians in Washington eager to serve as rubber stamps for his failed policy priorities and Columbia doesn't need another one."

The advertisements may serve as early defense for a governor considered an "overwhelming favorite" in November's election, said Gibbs Knotts, a politics professor at the College of Charleston.

"The economy has recovered somewhat in (South Carolina), and even more importantly, she is running in a state that Mitt Romney won by over 10 percentage points less than two years ago," he said. "Her main opponent, Vincent Sheheen, does have strong name recognition and some money, but far less than Haley, and he faces a lot of challenges running as a Democrat in a strongly Republican state. I suspect the RGA is just trying to guard its home turf with the ad buy, an insurance policy of sorts."

A recent poll conducted by Winthrop University also bolstered Haley, said Scott Huffmon, a Winthrop politics professor and poll director. The poll, which surveyed 901 likely Republican primary voters on a range of issues and races, showed that Haley has a 78 percent approval rating among those surveyed. The poll has a margin of error around 3 percent.

"This shows that Haley's support among the strongest segment of her base has solidified," Huffmon said.

Reach Jeremy Borden at 843-708-5837 or on Twitter @Jeremy_Borden.