Sen. Bernie Sanders Bernie SandersMcConnell accuses Democrats of sowing division by 'downplaying progress' on election security The Hill's Campaign Report: Arizona shifts towards Biden | Biden prepares for drive-in town hall | New Biden ad targets Latino voters Why Democrats must confront extreme left wing incitement to violence MORE’s (I-Vt.) campaign is at a crossroads after an onslaught of dispiriting losses to former Vice President Joe Biden Joe BidenCast of 'Parks and Rec' reunite for virtual town hall to address Wisconsin voters Biden says Trump should step down over coronavirus response Biden tells CNN town hall that he has benefited from white privilege MORE in the battle to be the Democratic presidential nominee.

The race is not over — Biden is still less than halfway to the 1,991 delegates he needs to clinch the nomination. But the math is grim for Sanders after he lost 10 of 14 states on Super Tuesday and was then routed in Michigan, Missouri and Mississippi this week.

A CNN analysis found Sanders would need to win the remaining states by an average of 10 points to catch Biden. Yet the map is getting tougher, as Sanders now faces the prospect of steep losses in Florida on March 17 and Georgia on March 24.

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Some Democratic party leaders have said it’s time for the primary to wind down, fearing that if Sanders lingers for too long it could damage Biden ahead of the race against President Trump Donald John TrumpHR McMaster says president's policy to withdraw troops from Afghanistan is 'unwise' Cast of 'Parks and Rec' reunite for virtual town hall to address Wisconsin voters Biden says Trump should step down over coronavirus response MORE in November.

Sanders on Wednesday said he intends to carry on and debate Biden on Sunday in Arizona. The final debate of the primary season will be the first time Sanders and Biden are on stage together in a one-on-one setting.

But Sanders made clear that his sole concern is defeating Trump, and he sent a strong signal that he would not do anything to harm the Democratic nominee in that pursuit.

“Trump must be defeated and I will do everything in my power to make that happen,” Sanders said.

Sanders’s speech was remarkable for its frankness about politics.

The Vermont senator declared that the progressive left had won the big policy battles of the day, but that Democratic voters had decided that Biden is the more electable candidate in a one-on-one matchup with Trump.

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“I strongly disagree with that assertion but that’s what millions of Democrats and independents are saying,” Sanders acknowledged.

Rather than attacking Biden’s record, Sanders laid out the policy questions that he wants the former vice president to address at their debate, such as his plans for health care, immigration, income inequality and criminal justice reform.

Notably, Sanders did not bring up past lines of attack over Biden’s vote to authorize military action in Iraq, a bankruptcy bill that critics say empowered the credit card industry, or Biden’s past statements about freezing Social Security.

Sanders instead opened the door for Biden to address the left’s concerns with his candidacy and to potentially begin to win over his fervent base of young supporters.

The remarks eased the fears of some Democrats, who were worried that Sanders might be preparing to go nuclear on Biden, damaging him ahead of the general election or provoking his base of young supporters to stay home on Election Day.

Sanders did not give a timeline or any insight into whether he’d stay in the race if Biden continues to pull away in the race for delegates. But his speech was cheered by even some of his longtime Democratic critics, who viewed it as a sober reading of the political landscape and a potential first step in uniting the party ahead of the general election.

“He said to Joe, issue by issue, question by question, here’s what you need to answer to get my support and to start to get my supporters to support you,” said Jon Reinish, a Democratic strategist in New York who supports Biden. “He very clearly laid that out and I thought it was remarkable … he was focused on how we unite to beat Donald Trump … I thought that was magnanimous, but also very, very smart.”

The speech was also well received by Sanders’s own supporters, who are eager to see him stay in the race to use his influence to ensure that progressives do not cede the gains they’ve made just because their candidate is not at the top of the ticket.

“Bernie should stay in the race and, in his ‘Joe is my friend but we disagree’ tone, continue to articulate the ideas that have shaped the Democratic debate for the past five years,” said Jonathan Tasini, a progressive strategist and Sanders supporter. “At the end of that road, as long as it takes, if millions of his supporters see meaningful embrace of a real Green New Deal, confronting corporate power and a path to universal government-provided healthcare, most will turn out in the general election as they did in 2016.”

Pressure began mounting on Sanders to wind down his candidacy as results rolled in on Tuesday night and Biden grew his delegate lead.

Rep. James Clyburn (D-S.C.), whose endorsement of Biden ahead of the South Carolina primary was a turning point in the race, said the next debate should be canceled.

Two Democratic super PACs declared Biden the presumptive nominee and said they’d refocus their efforts toward getting him elected in the fall.

Democratic strategist James Carville, a fierce Sanders critic, called on Sanders to drop out.

“This thing is decided, there's no reason to keep it going even a day longer,” Carville said.

But Sanders’s allies say that’s exactly the wrong message.

They believe Sanders’s supporters will turnout for Democrats against Trump, but that it will be better for the nominee to try to win them over on the merits, rather than to leave them feeling bullied into submission.

“The party has to be united to get rid of Trump, that’s the goal,” said Bill Press, a progressive thinker who supported Sanders early on in 2015. “To succeed in that goal, the party needs Bernie Sanders and his supporters. They need those young people, even if they’re not the majority, and the best way to piss them off would be to pressure Bernie out of this race. That’d be the biggest mistake they could make.”

“It doesn’t have to get nasty, and it shouldn’t get nasty or personal. I don’t think it has to be negative,” Press continued. “It’s just what the primaries are about, to let the people decide and not the poo-bahs. The best way to have a united party in November and to get the Bernie people out is to let them know that they’re really needed, not to dump on them.”

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In his victory speech on Tuesday night, Biden made his first overture to Sanders’s supporters.

“I want to thank Bernie Sanders and his supporters for their tireless energy and their passion,” Biden said in Philadelphia. “We share a common goal, and together we'll defeat Donald Trump.”