COLUMBIA, United States — Voters headed to the polls in South Carolina on Saturday for the fourth contest in the Democratic presidential nomination race, with Joe Biden looking to salvage his flagging White House hopes with a big win.

The former vice president is the firm favorite in the first state with a substantial African-American electorate to weigh in — but in nationwide polls he trails far behind frontrunner Bernie Sanders.

Both candidates will have a better picture of their overall prospects next week, when 14 states cast ballots on "Super Tuesday" — with a third of the delegates who formally choose the Democratic candidate to face President Donald Trump in November up for grabs.

Biden — the onetime race leader who failed to notch a win in Iowa, New Hampshire or Nevada — said he hopes South Carolina will propel him into national contention.

Voters have until 7:00 p.m. (2300 GMT) to make their choice.

"I think I'll do well," the 77-year-old Biden told CNN on Friday.

"It's been the launching pad for Barack and, I believe, for me," Biden added, referring to the nation's first black president and his boss for eight years, Barack Obama.

The stakes are high, analysts say.

"If Biden loses South Carolina, it would be a tremendous setback for his campaign, potentially disastrous," Kendall Deas, a political scientist at the College of Charleston, told AFP.

Biden leads in state polling, a dozen points ahead of Sanders and 20 points up on billionaire activist Tom Steyer, who is gunning for a third-place finish.

Steyer has spent an extraordinary $23.6 million on ads in South Carolina, nearly 10 times the number two spender, former Indiana mayor Pete Buttigieg, according to Advertising Analytics.

"I expect to surprise people by doing really well here," Steyer told CNN. "By doing really well with African-Americans."

At one polling place in a suburb of the state capital Columbia, about 20 people were lined up at 7:00 a.m. when the doors opened.

For 67-year-old retiree Samantha Rogers, who is black, Biden is the right candidate to take on Trump.

"He's more experienced. He's for all people, not just African Americans. He's for everyone," she told AFP.

But for 21-year-old student Andrea Green, "Bernie is telling the truth. He's authentic."

Biden and fellow moderates including Buttigieg and Senator Amy Klobuchar may well face a Sanders buzz saw come Super Tuesday, with the 78-year-old self-declared democratic socialist leading in the two biggest prizes, including crown jewel California.

Sanders is dominating there with 32.5 percent support, according to the RealClearPolitics polling average, with fellow progressive Senator Elizabeth Warren second.

Biden is a distant third with just 12.5 percent, in danger of missing the 15 percent threshold for earning delegates from the state.

In Texas, the other big Super Tuesday delegate gold mine, a new CNN poll there showed Sanders ahead of Biden by six points.

The senator also tops polls in Super Tuesday states Colorado, Maine, North Carolina, Utah, Virginia, his home state of Vermont and Warren's Massachusetts. Some of the races are tight.

With several Democratic establishment leaders fretting that Sanders could hold an insurmountable delegate lead after Tuesday, some have begun openly sounding the alarm.

South Carolina congressman James Clyburn, an influential black lawmaker who has endorsed Biden, warned of "down-ballot carnage" if the Democratic nominee is seen as too radical.

Buttigieg told MSNBC on Saturday that "I will do everything to make sure (Sanders) is the president if he's the nominee," but then added, "it's a harder sell than somebody focused to bring people together."

With party grandees desperate for a moderate to halt Sanders, the frontrunner punched back.

"One of the things the establishment is doing is, they're saying, 'Bernie can't beat Trump,'" Sanders told a crowd in St. George, South Carolina.

He pointed out that over the country's last 60 head-to-head polls with the incumbent, "we're ahead of Trump in 56 of them."

Sanders said his campaign will triumph "because we have an agenda that speaks to the needs of working-class people."

Rivals have mounted a fusillade of attacks against Sanders.

Among them were Mike Bloomberg, whose campaign aired ads slamming Sanders' gun rights voting record.

The centrist former New York mayor skipped the first four states in favor of making a splash on Super Tuesday.

Bloomberg, a billionaire media tycoon, has pumped a record $500 million into advertising, leading rivals to accuse him of seeking to "buy" his way into the race.

Biden has suggested Sanders would get trounced by Trump in southern states.

"Do you think running as a socialist would help you in Georgia, in North Carolina?" he said on CNN. "In South Carolina? In Texas?"

Trump put his own thumb on the scales Friday, at a rally in South Carolina.

"While we're building a great future, the radical Democrats are trying to burn it down," he told the crowd. — AFP