Former Vice President Joe Biden Joe BidenThe Memo: Warning signs flash for Trump on debates Senate Republicans signal openness to working with Biden National postal mail handlers union endorses Biden MORE’s campaign is looking to capitalize after a tremendous Super Tuesday, picking up new endorsements, raising big money and setting out for Missouri and Mississippi, where voters will cast ballots on Tuesday.

Biden got an immediate boost when former New York City Mayor Michael Bloomberg Michael BloombergThe Hill's 12:30 Report - Presented by Facebook - Latest with the COVID-19 relief bill negotiations The Memo: 2020 is all about winning Florida The Hill's Morning Report - Sponsored by The Air Line Pilots Association - Trump, Biden renew push for Latino support MORE dropped out of the race and endorsed him. The billionaire businessman, who spent more than $500 million on his own campaign, promised to do whatever he could to make Biden the next president.

The Biden campaign, which was strapped for cash only one week ago, raised $15 million in the three days after the South Carolina primary. The campaign said it’s experiencing a “tremendous surge” in online fundraising since Super Tuesday and would look for opportunities to expand its operations.

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Biden’s victories on Super Tuesday, and the centrist coalescence behind his campaign, was a relief to many Democratic officeholders, who have been unnerved by the rise of Sen. Bernie Sanders Bernie SandersSenate Republicans signal openness to working with Biden Hillicon Valley: DOJ indicts Chinese, Malaysian hackers accused of targeting over 100 organizations | GOP senators raise concerns over Oracle-TikTok deal | QAnon awareness jumps in new poll Schumer, Sanders call for Senate panel to address election security MORE (I-Vt.).

“We outperformed the most optimistic expectations and Sanders underperformed the most pessimistic expectations,” said Los Angeles Mayor Eric Garcetti (D), a co-chairman for Biden’s campaign. “The blue wave voters who flipped the House [for Democrats] in 2018 turned out in large numbers last night and we overwhelmingly won their support.”

The race is not over.

Vote counting is still underway in California, the biggest delegate prize in the country, where Sanders is on pace to win comfortably.

Biden campaign officials estimated that they’d come out of Super Tuesday with a lead of about 50 delegates, giving the former vice president an unexpected but not insurmountable lead.

Sanders said the race could be closer than that.

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“My guess is that after California is thrown in the hopper we may be up by a few, Biden may be up by a few, but I think we now go forward basically neck and neck,” Sanders said at a press conference in Vermont.

There will not be a Democratic presidential debate between now and next Tuesday, when voters in Michigan, Idaho, Mississippi, Missouri, North Dakota and Washington state hold primaries.

Sanders has a lot riding on the primary in Michigan, the largest state to vote next week with 125 delegates up for grabs. Sanders won Michigan in 2016, but it could be tough terrain for him this time around. Polls showed Bloomberg had significant support there, which could move behind Biden.

Sanders will hold rallies in Detroit and Grand Rapids this week and plans to highlight Biden’s support for trade deals that he says have been harmful to working-class voters in the state.

“The Midwest has been hard hit by disastrous trade agreements,” Sanders said. “Joe is going to have to explain to the people and union workers why he supported those disastrous trade agreements.”

The Biden campaign is bracing for what looks like a one-on-one contest with Sanders, as Sen. Elizabeth Warren Elizabeth WarrenNo new taxes for the ultra rich — fix bad tax policy instead Democrats back away from quick reversal of Trump tax cuts It's time for newspapers to stop endorsing presidential candidates MORE (D-Mass.) feels pressure on the left to bow out of the race.

Warren met with advisers on Wednesday to consider her way forward, but there is no guarantee her supporters would shift directly behind Sanders if she did drop out.

The Sanders campaign is signaling a new approach, releasing an ad touting Sanders’s relationship with former President Obama, who has not endorsed a candidate in the race.

But Sanders is also ramping up his attacks on Biden.

The campaign released another ad on Wednesday accusing Biden of supporting cuts to Social Security, going directly after the older voters who have backed the former vice president in large numbers.

At his Burlington press conference, Sanders attacked Biden for not supporting "Medicare for All," for his vote to authorize military action in Iraq and for policies he says have benefitted the credit card companies and Wall Street.

The Biden campaign fears that the showdown with Sanders will become a rerun of the divisive 2016 primary between Sanders and former Secretary of State Hillary Clinton Hillary Diane Rodham ClintonBarr criticizes DOJ in speech declaring all agency power 'is invested in the attorney general' Virginia Democrat blasts Trump's 'appalling' remark about COVID-19 deaths in 'blue states' The Hill's Campaign Report: Biden asks if public can trust vaccine from Trump ahead of Election Day | Oklahoma health officials raised red flags before Trump rally MORE.

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“We’ve seen what kinds of campaigns Bernie Sanders runs and the impact it had on 2016,” said Biden deputy campaign manager Kate Bedingfield.

Sanders has been energizing his base of supporters around the idea that the Democratic establishment has banded behind Biden in an effort to stop him.

On Wednesday alone, Biden picked up endorsements from Bloomberg and Reps. Mike Quigley Michael (Mike) Bruce QuigleyDemocrats introduce legislation to revise FDA requirements for LGBT blood donors Tucker Carlson sparks condemnation with comments about deadly Kenosha shooting Hillicon Valley: Three arrested in Twitter hack | Trump pushes to break up TikTok | House approves 0M for election security MORE (D-Ill.), Robin Kelly Robin Lynne KellyRep. Robin Kelly enters race for Democratic caucus vice chair Hillicon Valley: Oracle confirms deal with TikTok to be 'trusted technology provider' | QAnon spreads across globe, shadowing COVID-19 | VA hit by data breach impacting 46,000 veterans House approves bill to secure internet-connected federal devices against cyber threats MORE (D-Ill.), Bill Foster George (Bill) William Foster81 Nobel laureates endorse Biden's White House bid Trump payroll tax deferral finds few takers among businesses Former Obama Ebola czar Ron Klain says White House's bad decisions have put US behind many other nations on COVID-19; Fears of virus reemergence intensify MORE (D-Ill.), Kathy Castor Katherine (Kathy) Anne CastorOVERNIGHT ENERGY: Democrats push resolution to battle climate change, sluggish economy and racial injustice | Senators reach compromise on greenhouse gas amendment stalling energy bill | Trump courts Florida voters with offshore drilling moratorium Trump courts Florida voters with moratorium on offshore drilling Lawmakers, public bid farewell to John Lewis MORE (D-Fla.) and Lois Frankel Lois Jane FrankelShakespeare Theatre Company goes virtual for 'Will on the Hill...or Won't They?' Florida Democrat introduces bill to recognize Puerto Rico statehood referendum Hillicon Valley: Democrats demand answers over Russian interference bulletin | Google Cloud wins defense contract for cancer research | Cyberattack disrupts virtual classes MORE (D-Fla.), as well as Rhode Island Gov. Gina Raimondo (D), who had previously backed Bloomberg.

Over the past 48 hours, Biden has also been endorsed by four former Democratic presidential candidates.

“What this campaign is increasingly about is which side are you on,” Sanders said. “There has never been a campaign in recent history to take on the entire political establishment, an establishment that is working furiously to try and defeat us.”

The Biden campaign lashed out at Sanders for casting him as the establishment’s preferred candidate, pointing to Biden’s massive margins among black voters in the South, who have powered him to victory in South Carolina, Alabama, Virginia and North Carolina.

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“I didn’t know African Americans in the South are considered part of the establishment,” said Rep. Cedric Richmond Cedric Levon RichmondRep. Cedric Richmond set to join House Ways and Means Committee Biden campaign ratchets up courting of Black voters, specifically Black men Buttigieg, former officials added to Biden's transition team MORE (D-Va.), a co-chairman for the Biden campaign and chairman of the Congressional Black Caucus.

Biden this week will head straight for Mississippi, a state that is nearly 40 percent African American. After that, Biden will travel to Missouri, another state holding a contest on Tuesday.

The Biden campaign should have more freedom in the coming days to add staff and open new offices across the country, something it was unable to do before Super Tuesday.

Sanders, meanwhile, opened four new offices in Missouri on Wednesday.

After Michigan, Sanders will head to Arizona and Illinois, where voters will cast ballots on March 17.

There will be a debate — potentially between only Biden and Sanders — on March 15.

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Sanders’s allies were shaken by Tuesday’s results but still see a path to the nomination for their candidate.

“Bernie and his movement do their best work as underdogs,” said Neil Sroka, a strategist with the progressive group Democracy for America. “The political elite underestimate him at their own peril.”

The Biden campaign said it wouldn’t take anything for granted after its sudden success.

“Anyone who thinks we won’t keep campaigning like we’re underdogs is wrong,” said Garcetti. “That’s what this campaign is all about.”