The character actor Reg E. Cathey, best known for portraying Freddy Hayes of Freddy’s barbecue restaurant in the Netflix drama “House of Cards,” has narrated several ads for Senator Bernie Sanders.

Now, as the Democratic primary intensifies in South Carolina, Mr. Cathey’s resonant voice is about to get some competition from the actor known as Hollywood’s voice of God.

Morgan Freeman has lent his voice to Hillary Clinton’s presidential campaign, narrating in his deep, languid way several ads that will begin airing in South Carolina ahead of the state’s Feb. 27 Democratic primary.

The first ad, titled ”All the Good,” opens with a scene of a church, empty pews filling the screen. Images of Mrs. Clinton working with children appear, as Mr. Freeman says, “Her church taught her to do all the good you can for all the people you can, for as long as you can.”

The rest of the footage shows Mrs. Clinton in various stages of her career as the actor narrates. “After law school, she could have joined a high-priced law firm, but instead she worked to reform juvenile justice in South Carolina,” Mr. Freeman says. “Her life’s work has been about breaking barriers and so would her presidency.”

Mr. Freeman, whose voice has been the powerful backdrop of movies like “The Shawshank Redemption” and “Million Dollar Baby,” has served as a campaign surrogate for Democrats in the past.

The ad he narrated for President Obama’s 2012 re-election campaign, “Challenges,” was widely considered among the most effective from that cycle. “Every president inherits challenges, few have faced so many,” Mr. Freeman says.

The ad for Mrs. Clinton, which will be rolled out with a CNN interview with Mr. Freeman on why he is supporting her, comes at a critical time for her campaign.

Both Mrs. Clinton and Mr. Sanders are courting black voters, and while Mr. Freeman does not emphasize race in the ad or in his endorsement, the Academy Award winner’s support will lend a familiar and authoritative tone to her campaign’s message.