The first official pro-Hillary Clinton ad in South Carolina is hitting airwaves this week, and it features former Attorney General Eric Holder making the case that Clinton is the best candidate to carry on President Barack Obama's legacy.

"If you want to make sure Republicans don’t take us backward, help Hillary move us forward," Holder says in the 30-second advertisement.

Clinton has been working hard to convince Obama supporters that she -- not her primary opponent, Sen. Bernie Sanders (I-Vt.) -- will move the president's work forward. She has accused Sanders of wanting to undo Obamacare and instead implement a single-payer health care plan, and has defended the president's legacy of taking on Wall Street. 

In the ad, Holder specifically mentions Clinton's push to strengthen gun laws and police accountability. Clinton has accused Sanders of being too weak in standing up to gun manufacturers. 

South Carolina's Democratic primary on Feb. 27 will be the fourth in the nation. The state has a sizable population of politically active black voters -- a constituency with which Clinton still holds a lead but with which Sanders is trying to make inroads. 

The TV spot is scheduled to air this week in Charleston, Columbia, Greenville-Spartanburg and Florence-Myrtle Beach.