Joe Biden scrambled to salvage his flagging presidential hopes Friday on the eve of South Carolina's Democratic primary, where nothing less than a decisive victory can help him rebound and challenge frontrunner Bernie Sanders.
The former vice president is the firm favourite in the first state in the race with a substantial African-American Democratic electorate -- but trails far behind the surging leftist in nationwide polls.
Both candidates will have a better picture of their prospects just days after South Carolina, with 14 states voting on "Super Tuesday" and a third of the delegates who formally choose the Democrat to face President Donald Trump in November up for grabs.
Biden, the former frontrunner who failed to notch a win in the first three states, said he hopes South Carolina will propel him into national contention.
"I've worked hard to earn these votes, and I think I'll do well," the 77-year-old told CNN early Friday, before heading to a trio of 11th-hour events.
"It's been the launching pad for Barack and I believe for me," Biden added, referring to the nation's first black president Barack Obama.
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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 USD 23.6 million on ads in South Carolina, nearly 10 times the number two spender, former Indiana mayor Pete Buttigieg, according to Advertising Analytics.
Some polling has been misleading in the early contests. In Iowa for instance, Biden was second in polls before caucus night but finished fourth.
Biden and fellow moderates including Buttigieg and Senator Amy Klobuchar may well face a Sanders buzz 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 per cent support, according to the RealClearPolitics polling average, with fellow progressive Senator Elizabeth Warren second.
Biden is a distant third with just 12.5 per cent, in danger of missing the 15 per cent threshold for earning delegates from the state.
Sanders recently eclipsed Biden in Texas, the other big delegate gold mine, and expanded his lead there after a CNN poll showed him ahead of Biden by 26 per cent to 20 per cent.
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 Super Tuesday, some have begun openly sounding the alarm.
Senator Tim Kaine of Virginia, the 2016 vice presidential nominee, endorsed Biden Friday, tweeting that "Joe has exemplary heart, character, and experience" to be commander-in-chief.
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.
With party grandees desperate for a moderate to halt Sanders, the frontrunner punched back to say his campaign is best positioned to win.
"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".
Brenda Roi, a voter at a Sanders rally Friday in Columbia, said she ignores the establishment and its "scare tactic" aimed at sinking Sanders.
"The establishment is going to say those things because they want to keep things the way they are," the 49-year-old told AFP. "They know full well that he can beat Trump."
"Do you think running as a socialist would help you in Georgia, in North Carolina?" Biden said on CNN. "In South Carolina? In Texas?"