HILTON HEAD, S.C. — Joe Biden expressed confidence on Monday that he would win this weekend’s South Carolina primary as he and other Democrats fight to loosen front-runner Bernie Sanders’ grip on the party’s 2020 presidential nomination.

Opening the most critical week of his campaign, Biden said he would win “by plenty” in Saturday’s contest in South Carolina, the first state with a sizable black population to weigh in on the Democratic race.

“I know I can,” Biden said when asked whether he can notch his first victory of the primary season.

No state holds more sway over the former vice president’s political future. Biden is betting that a strong showing among African American voters will give his campaign the needed boost to recover from disappointing finishes in Iowa and New Hampshire earlier this month. His allies acknowledge he must win South Carolina to have any chance of reviving his campaign.

Even in this state, the focus is shifting to Sanders. The self-described democratic socialist scored a commanding win in Nevada over the weekend, giving him two consecutive victories after a tie with Pete Buttigieg in Iowa. Sensing the prospect of a knock-out punch in South Carolina, Sanders is ramping up his own outreach in the state.

His rivals moved quickly to try to blunt his efforts.

Speaking to more than 100 at a breakfast on Monday in Hilton Head, billionaire activist Tom Steyer warned “we can’t nominate someone who is going to divide us.”

Asked by a voter how he would beat Sanders, Steyer declared himself just as progressive as the Vermont senator.

“In lots of things, I’m more progressive than Bernie Sanders,” said Steyer, who has spent millions from his personal fortune to combat climate change and encourage President Donald Trump’s impeachment.

Steyer has spent more money than his seven rivals combined on television advertising in South Carolina, potentially peeling off support from Biden and Sanders.

The fiercest attacks on Sanders came from another billionaire, Mike Bloomberg. The former New York mayor won’t be on the South Carolina ballot, but has publicly warned that Sanders could amass an unbeatable delegate lead on Super Tuesday — in just eight days — unless he’s stopped.

Bloomberg attacked Sanders on multiple fronts, including his record on gun control. Representing a rural state where gun ownership is high, Sanders enjoyed the backing of the NRA early in his decades-long congressional career, although he proudly proclaims his F rating now.

“The NRA paved the road to Washington for Bernie Sanders,” Bloomberg tweeted. He added: “We deserve a president who is not beholden to the gun lobby.”

Sanders was also facing blowback from critics in both parties for comments that aired Sunday on CBS’ “60 Minutes” about the late Cuban dictator Fidel Castro.

“We’re very opposed to the authoritarian nature of Cuba but you know, it’s unfair to simply say everything is bad, you know?” Sanders said on the program. “When Fidel Castro came into office, you know what he did? He had a massive literacy program. Is that a bad thing? Even though Fidel Castro did it?”

Rep. Donna Shalala, D-Fla., was among Sanders’ vocal critics.

“I’m hoping that in the future, Senator Sanders will take time to speak to some of my constituents before he decides to sing the praises of a murderous tyrant like Fidel Castro,” the first-term Democrat tweeted.

Sanders was also in a dispute with the Anti-Defamation League, an establishment group that advocates for strong U.S.-Israel relations. Sanders said he would skip the group’s conference because he was concerned about the event giving airtime to “leaders who express bigotry and oppose basic Palestinian rights.”

Jonathan Greenblatt, the group’s CEO, called that characterization “offensive” and “irresponsible.”

Watching the tumult from afar during a trip to India, Trump predicted a long and messy primary season for his rivals.

“It could go to the convention, it really could,” Trump said. “They are going to take it away from Crazy Bernie, they are not going to let him win.”

He added: “I actually think he would be tougher than most of the other candidates because he is like me but I have a much bigger base.”

Some Democratic Sanders opponents were worried that the new focus may be too little, too late.

For months, as several Democrats jockeyed to become the chief alternative to Sanders, they largely attacked each other on debate stages and in ads while taking relatively few punches at the Vermont senator.

Indeed, even after Sanders’ strong victory in Nevada, progressive Sen. Elizabeth Warren avoided launching a direct hit at Sanders even when asked whether a Sanders nomination would be a risk for the Democratic Party.

Speaking to reporters in Denver, Warren instead continued her attacks on Bloomberg, calling him the “riskiest candidate standing on that stage because of his history of hiding his taxes, his history of harassment of women and his history of defending racist policies.”

The anti-Sanders efforts may peak on the debate stage Tuesday night in South Carolina.

Bloomberg asked to delay a CNN town hall initially planned for Monday until Wednesday to spend more time preparing for the debate. He badly stumbled last week in his debate debut.

“The country can’t afford to let Bernie Sanders skate by another debate without a focus on his extreme record,” said Bloomberg spokesperson Galia Slayen.

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