The morning after his first presidential primary win in the 2020 race, Joe Biden insisted he hasn’t exhausted his campaign in South Carolina. However, doubts emerged that he can compete against a crowded Democratic field led by Bernie Sanders.

Mr Biden announced a $5m (£4m) fundraising surge as his campaign looks to build on his South Carolina win with positive results in crucial Super Tuesday elections, but his relatively late boost is nowhere near Mr Sanders’ fundraising. The Vermont senator’s campaign says it raised more than $46.5m from more than 2.2m individual donations in February alone.

Mr Sanders also has a double-digit lead ahead of the former vice president in early polls in delegate-rich Texas. The candidates are neck and neck in North Carolina, among the 14 states that hold their primaries on 3 March, vying for a share of nearly one-third of all delegates that will select the nominee at the party’s convention this summer.

Asked whether moderate candidates need to drop out to consolidate their votes around the former vice president, Mr Biden told CNN that he “hasn’t had any conversations along those lines” but claimed that “it’s going to be much more difficult to win back the Senate and keep the house if Bernie Sanders is at the top of the ticket”.

On NBC, Mr Biden called Sanders’ policies “very controversial”, pointing to his signature Medicare for All healthcare plan, and insisted that voters “are not looking for revolution, they are looking for results, they’re looking for change, they’re looking for movement forward”.

Democratic candidates compete on the campaign trail: In pictures Show all 18 1 /18 Democratic candidates compete on the campaign trail: In pictures Democratic candidates compete on the campaign trail: In pictures Jessica Canicosa, a precinct captain for Bernie Sanders, waits to greet caucus voters at Liberty High School in Henderson, Nevada REUTERS Democratic candidates compete on the campaign trail: In pictures Hotel workers at the Bellagio in Las Vegas get to grips with voting papers during the Nevada caucuses AFP via Getty Images Democratic candidates compete on the campaign trail: In pictures A caricature of Bernie Sanders is projected on to a tree during a rally in Las Vegas EPA Democratic candidates compete on the campaign trail: In pictures A woman waits to have a photo taken with Elizabeth Warren during a town hall meeting in Las Vegas REUTERS Democratic candidates compete on the campaign trail: In pictures The threat of coronavirus and other germ-borne illnesses was on some voters' minds at the Democratic caucuses in Henderson, Nevada Getty Images Democratic candidates compete on the campaign trail: In pictures Former vice-president Joe Biden takes a selfie with a voter in Las Vegas ahead of the Nevada caucuses REUTERS Democratic candidates compete on the campaign trail: In pictures Amy Klobuchar changes her shoes backstage after giving a speech in Exeter, New Hampshire AFP/Getty Democratic candidates compete on the campaign trail: In pictures A warmly-wrapped-up dog attends an Elizabeth Warren event at Amherst Elementary School in Nashua, New Hampshire AFP/Getty Democratic candidates compete on the campaign trail: In pictures Bernie Sanders, who romped to victory in New Hampshire against Hillary Clinton in 2016, talks to the media in Manchester Getty Democratic candidates compete on the campaign trail: In pictures Joe Biden was hoping to improve on his poor showing in Iowa in the New Hampshire primary Reuters Democratic candidates compete on the campaign trail: In pictures Elizabeth Warren, renowned for giving time to supporters for selfies, works the crowd at the University of New Hampshire in Durham Getty Democratic candidates compete on the campaign trail: In pictures Joe Biden takes a selfie with a supporter and his child outside a campaign event in Somersworth, New Hampshire on 5 February Reuters Democratic candidates compete on the campaign trail: In pictures Elizabeth Warren and Bernie Sanders quarrel after a confrontation in a TV debate in which Sanders claimed that Warren was not telling the truth about a conversation in which she claimed he had said a woman could not win the presidency on 14 January AP Democratic candidates compete on the campaign trail: In pictures Supporter Pat Provencher listens to Pete Buttigieg in Laconia, New Hampshire on 4 February Getty Democratic candidates compete on the campaign trail: In pictures Pete Buttigieg speaks at a campaign event in Concord, New Hampshire while awaiting the results of the Iowa caucus Reuters Democratic candidates compete on the campaign trail: In pictures Elizabeth Warren is presented with a balloon effigy of herself at a campaign event in Nashua, New Hampshire on 5 February Reuters Democratic candidates compete on the campaign trail: In pictures A Trump supporter rides past a rally for Amy Klobuchar in Des Moines, Iowa on 14 January AP Democratic candidates compete on the campaign trail: In pictures A man holds up a sign criticising billionaires in the presidential race in front of Michael Bloomberg in Compton, Califronia. The former New York mayor skipped the first caucus in Iowa and instead campaigned in California on 3 February Reuters

But exit polls in Biden-favoured South Carolina showed that a majority of Democrats in the state support Medicare for All, while Mr Biden trails Mr Sanders in several national polls ahead of Tuesday’s votes.

Asked if he believed Donald Trump would defeat Mr Sanders if he became the party’s nominee, Mr Biden said: “I do.”

“Everybody’s going to look at Bernie’s record as closely as they’ve looked at mine over the last five months, and I think they’re going to see some stark differences in where we stand,” Mr Biden said.

Mr Biden’s win in South Carolina was fuelled by his relationships with vital political figures in the state, and the backing of older moderate black voters, giving him a dominant 44-point lead against Mr Sanders, who captured 17 per cent of black voters compared to Mr Biden’s 61 per cent.

Mr Sanders won with black voters under 30, however, underlining the not-so-monolithic utility of candidates’ reliance on “the black vote” in the 2020 election.

Asked by Chuck Todd on NBC’s Meet the Press how he plans to sustain that kind of support nationwide, as Mr Sanders overtook the candidate in Super Tuesday polls, Mr Biden said: “Just watch me.”

“I take nothing for granted”, he said. “But if we win, it’s going to be because of the message we have and because we’re going to get something done.”

Mr Biden said he believes he can emerge as the victor before the convention.

He said: “We’re moving into constituencies that, when they hear me, have always been mine – diverse communities: white, working-class folk, African Americans and Hispanics, people in the middle class, women in the suburbs. There are places I’ve always been very strong my whole career.”

Fox News host Chris Wallace challenged his success in the south, pointing out that the candidate hasn’t held a rally in a Super Tuesday state in more than a month and only started running television ads in California this past week, while the Sanders campaign has spent more than $13m.

Wallace asked Mr Biden what his campaign will do if he’s “clobbered” on Tuesday.