Former U.S. Vice President Joe Biden, 2020 Democratic presidential candidate, right, greets House Majority Whip James Clyburn, a Democrat from South Carolina, during Jim Clyburn's World Famous Fish Fry event in Columbia, South Carolina, June 21, 2019.

NORTH CHARLESTON, S.C. — Joe Biden just got a boost in the state that will shape the fate of his presidential bid.

Rep. James Clyburn, a South Carolina Democrat and the top ranking African American in the House, endorsed the former vice president on Wednesday. White House hopefuls have sought the support of the House majority whip, who holds major sway in the Palmetto State, where blacks represent a powerful voting bloc.

"I want the public to know that I'm voting for Joe Biden. South Carolinians should be voting for Joe Biden," he said in remarks from North Charleston.

"I know Joe. We know Joe. But most importantly, Joe knows us," he added.

The endorsement gives Biden a bump just days before Saturday's South Carolina primary. Biden, following a string of disappointing finishes in the first three primary nominating contests, sees winning the state as pivotal to reviving his once-promising push for the Democratic nomination.

At Tuesday night's debate, he predicted he would win Saturday's primary.

The former vice president, who served under President Barack Obama, has enjoyed strong support among African American voters. They make up a majority of South Carolina's Democratic primary electorate. His support in the state has waned, as he had only a narrow lead over Sen. Bernie Sanders in the latest NBC News/Marist poll of South Carolina.

The endorsement came minutes after Clyburn and Biden shared a stage at Mount Moriah Missionary Baptist Church in South Carolina for the National Action Network Ministers Breakfast.

Biden said in a brief speech in front of a nearly entirely black audience that Clyburn was among the best people he knew in either private or public life. He also played up his connections to Obama, at one point apologizing for calling him "Barack." He noted that Obama was a friend.

In later remarks following Clyburn's endorsement, Biden took apparent shots at Sanders, who has called for a "political revolution." The former vice president has contended most Americans will not embrace the Vermont senator's proposals such as a single-payer "Medicare for All" system.

"Today, people are talking about a revolution," Biden said. "What the country's looking for are results. What they're looking for is security."

Interviews with voters at the breakfast suggested many had not made up their minds Wednesday.

One woman, who asked not to be named because she said she was not "seeking celebrity," said she is definitely voting Saturday. She added her choice would be based on "only what I hear from the Spirit."

She said she was deciding between Sen. Elizabeth Warren, D-Mass., and Biden. She also likes former New York Mayor Mike Bloomberg, who will not appear on the ballot Saturday.

Another black woman, Evett Simmons, who supports Sen. Amy Klobuchar, brushed off the idea that moderates should rally around one candidate to take on Sanders.

"In two weeks I may have a different opinion," she said.

— CNBC's Tucker Higgins reported from North Charleston, S.C., and Jacob Pramuk reported from Englewood Cliffs, N.J.

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