The 30-second ad, titled "Leader," features clips of Romney touting his "steadiness and constancy." It previously aired in Iowa and New Hampshire.
"If I'm president of the United States I will be true to my family, to my faith and to our country, and I will never apologize for the United States of America," Romney says in a clip taken from a GOP debate.
This is the first official campaign ad to appear in South Carolina, reports The State.
South Carolina Gov. Nikki Haley (R) endorsed Mitt Romney for president Friday.
"Today is the day that I am throwing all of my support behind Mitt Romney for president," Haley said on Fox News.
The South Carolina primary takes place next month. Romney has held a lead for the GOP presidential nomination in polls for much of the year, but has recently seen former House Speaker Newt Gingrich (Ga.) surpass him in national polls and in surveys of Iowa caucus-goers.