WASHINGTON - In his third run for the U.S. presidency, former Vice President Joe Biden is fighting for his political life.

But possible signs that he could win Saturday's key Democratic presidential primary in South Carolina give him a chance in the long string of nominating contests that follow in March.

Biden confidently declared at Tuesday night's Democratic presidential debate that he would win the southern state, and some polls support his claim. Polling website fivethirtyeight.com shows Biden winning about 30% of the vote, followed by national front-runner Bernie Sanders with 23%, and Tom Steyer, a wealthy long shot, polling third at 13%.

Biden, with longtime support from African American voters, is hoping to win in a state where blacks could comprise more than half of the Democratic vote. He has been touting his experience as second in command for eight years under the country's only black president, Barack Obama. On Wednesday, a key black lawmaker from the state, Congressman James Clyburn, endorsed Biden's candidacy."

I've been saying to the media, I've known for a long time who I'm going to vote for," Clyburn said. "But I want the public to know that I'm voting for Joe Biden. South Carolina should be voting for Joe Biden."

Biden once led national polls of Democratic voters as the candidate with the best chance to oust Republican President Donald Trump. But Sanders, a longtime senator from the northeastern state of Vermont and a self-declared democratic socialist, has pushed Biden to second place in national polls after winning the popular vote in the first three party nominating contests this month.

Meanwhile, Biden finished fourth in Iowa, fifth in New Hampshire and a distant second to Sanders last Saturday in Nevada.

U.S. political analysts credited Biden with a strong debate performance, but verbal gaffes marred his performance.

While promoting his support for gun control legislation, Biden mistakenly said that 150 million Americans had been shot to death in recent years, a staggering number that involved nearly half the U.S. population. His campaign later acknowledged that the correct number was 150,000 people.

Trump, assessing the Democratic candidates, took note of Biden's mistake.

"Crazy, chaotic Democrat Debate last night. Fake News said Biden did well, even though he said half of our population was shot to death. Would be OVER for most," he tweeted.

Whatever Biden's fate in South Carolina, he and the other Democratic candidates face an immediate new challenge on Super Tuesday, when 14 states hold Democratic nominating contests to pick delegates to the party's national convention in July.

While 54 delegates are in play in South Carolina, a total of 1,357 are at stake on Super Tuesday, when former New York Mayor Michael Bloomberg appears on the ballot for the first time. The one-day voting marathon accounts for a third of the delegates.

Because Democrats award national delegates based on the proportion of the vote the candidates claim in each state, several contenders could win a sizable delegate count.

But based on polling, fivethirtyeight predicts Sanders could win 587 pledged delegates on Tuesday. Biden could win 305; Bloomberg, 211; and Massachusetts Sen. Elizabeth Warren, 132.

Such a result would put Sanders in a commanding position to eventually claim the Democratic presidential nomination, although nowhere near the 1,990-delegate majority any of the candidates need. A large Sanders lead after Super Tuesday could also force out weaker performing candidates.