HOUSTON (AP) — Rivals no more, Amy Klobuchar and Pete Buttigieg united behind Joe Biden’s presidential bid on Monday as the Democratic Party’s moderate wing scrambled to boost the former vice president just hours before voting began across a series of high-stakes Super Tuesday states.

The urgency of the moment reflected deep concerns from the Democratic establishment that Bernie Sanders, a polarizing progressive, was positioned to seize a significant delegate lead when 14 states, one U.S. territory and Democrats abroad vote on Tuesday.

Klobuchar formally suspended her campaign and endorsed Biden on Monday, a day after Buttigieg announced his formal exit. Both Klobuchar and Buttigieg, who had been Biden’s chief competition for their party’s pool of more moderate voters over the last year, were set to announce their support for Biden later Monday at a rally in Dallas.

Buttigieg’s plans were confirmed by two people familiar with the decision who were not authorized to speak publicly and spoke to The Associated Press on condition of anonymity.

Klobuchar and Buttigieg become the second and third Democrat to abandon their presidential bids since Biden scored a resounding victory in South Carolina, his first of the 2020 roller-coaster nomination fight.

Sanders’ senior strategist Jeff Weaver dismissed the importance of the new coalition, which he said would help highlight the divide between the true progressive wing of the party and those in the establishment.

“It’s becoming increasingly clear that the candidates funded by big money and super PACs are coalescing behind Joe Biden, and that’s not a surprise,” Weaver said. “I think it’ll add a lot of clarity to this race.”

A shrinking group of other Democrats vowed to press on, potentially toward a contested convention.

The fast-moving developments came at a key crossroads in the Democratic Party’s turbulent primary season. The states that vote on Tuesday, led by California and Texas, offer almost 10 times as many delegates in a single day than have been awarded over the first month.

Sanders remained the undisputed front-runner. But the rest of the field was decidedly unsettled, even after Biden’s South Carolina blowout and the departures of Klobuchar, Buttigieg and billionaire activist Tom Steyer.

New York billionaire Mike Bloomberg in particular could create problems for Biden’s establishment appeal. Bloomberg, who will appear on a 2020 ballot for the first time on Tuesday, has invested more than a half billion dollars into his presidential bid and wracked up many high-profile endorsements of his own.

Yet Biden appeared to have the momentum on the eve of Super Tuesday after his blowout South Carolina victory.

The Biden campaign reported back-to-back days of $5 million fundraising hauls, by far the best 48-hour stretch of his campaign. Biden himself touted the threshold Sunday night on a call with donors, according to one person on the call.

And the campaign highlights several new endorsements. Perhaps the most powerful endorsement would come from former President Barack Obama, who has a relationship with most of the candidates and has talked with several in recent weeks as primary voting has begun. He spoke with Biden to congratulate him after his South Carolina victory, but still has no plans to endorse in the primary at this point.

Yet a stream of new Biden backers stepped forward in the run-up to Tuesday, including former Nevada Sen. Harry Reid. The former Senate majority leader said, “I believe Biden is best able to defeat Donald Trump and enact the policies we all care about.”

Biden’s growing collection of endorsers also features Obama national security adviser Susan Rice; former Colorado Sen. Mark Udall; former California Sen. Barbara Boxer; Rep. Jennifer Wexton, D-Va.; Illinois Secretary of State Jesse White; former Arkansas Sen. Blanche Lincoln; and Rep. Gil Cisneros, D-Calif.

Virginia Rep. Don Beyer, the first member of Congress to endorse Buttigieg, said he planned to endorse Biden and expected Buttigieg to as well.

“I do think it’s the most logical,” Beyer said of a Biden endorsement, given his echo of the former vice president’s call for civility, a mantra of the Buttigieg campaign. “I think Joe is the next best possibility.”

While Biden clearly has momentum, not everyone in his party’s moneyed establishment is convinced.

Across the country, some major donors remain skeptical and want to see what happens on Super Tuesday before deciding whether to support Biden.

Biden has struggled to raise money in Silicon Valley, for example. The area is dominated by the tech sector, and many of its wealthy donors prioritize executing a data-driven plan. Biden’s rocky campaign pushed many toward Buttigieg or Bloomberg in recent months, financiers say. Biden’s team is waging a quiet campaign to win them over, yet many are taking a wait-and-see approach.

“We need to see what happens tomorrow, which is going to be very telling,” said Alex Sink, a Democratic donor and former Florida gubernatorial candidate who endorsed Bloomberg.

During a round of weekend interviews, Biden pledged to improve his campaign organization, his fundraising operation and even his own performance.

He reliance on media coverage, instead of a round of Super Tuesday advertising, reflected a stark reality a day after his resounding primary victory in South Carolina: The former vice president was forced to rely on free media coverage because he was understaffed, underfunded and almost out of time as he fought to transform his sole win into a national movement.

Biden allies conceded that the post-South Carolina fundraising surge would have little impact on Super Tuesday.

“Super Tuesday is too close,” said former Pennsylvania Gov. Ed Rendell, a Biden supporter. “Fortunately, Joe Biden has been on the national scene for 35 years. He has less need to advertise.”

Meanwhile, Sanders was focused on California, the crown jewel of Super Tuesday. California alone offers 415, which is more than double the amount of delegates allocated through Iowa, New Hampshire, Nevada and South Carolina.

Sanders predicted victory in California as he rallied thousands of supporters in multiple stops and attacked Biden’s record on foreign policy, trade and Social Security, among other issues.

“My point here is not just to be negative about Joe,” Sanders said. “My point here is to ask you: ‘What campaign is going to beat Donald Trump?’”

Sanders has struggled to win over many elected officials in Washington but earned a high-profile endorsement Monday from Democracy for America, a national grassroots organization originally led by former Vermont Gov. Howard Dean, that boasts thousands of members across the county.

“The overwhelming support for Bernie we saw in our member vote should be a wake-up call to the broken, visionless, corporate Democratic establishment,” said the organization’s chair Charles Chamberlain. “American’s want fundamental change in Washington, not a return to the status quo.”

The future for candidates not named Biden or Sanders appeared uncertain at best.

A handful of high-profile political strategists with ties to the former president encouraged Biden’s rivals — including Bloomberg — to quit the race to allow anti-Sanders Democrats to unify behind Obama’s former vice president.

“Most of them have seen the writing on the wall for at least the last week,” said Rufus Gifford, who held top fundraising posts on both of Obama’s presidential campaigns and was part of Biden’s fundraising operation. “It’s clear the Democratic alternative to Bernie Sanders is Joe Biden.”

But in an example of Biden’s challenge ahead, Sanders said Sunday he raised an eye-popping $46.5 million for February. That compared to $29 million for Warren and $18 million for Biden over the same period.

In addition to his phone call with Biden, Buttigieg also spoke with Obama, who has been calling most of the candidates who have departed the race.

Obama praised Buttigieg’s campaign and his decision to step aside at this critical juncture in the Democratic primary, according to a person with knowledge of the call. The person, like the one on the Biden fundraising call, spoke on condition of anonymity to describe internal matters.

Biden’s other rivals showed no interest in getting out of the race. In fact, some vowed to keep fighting no matter what happened on Super Tuesday.

Warren campaign manager Roger Lau spoke brazenly of pushing into a floor battle at the Democratic National Convention this summer if no candidate emerged from the primary season with a clear majority, which was possible even if someone had a large delegate lead.

“The convention in Milwaukee is the final play,” Lau wrote in a Sunday memo.

And Bloomberg, who this week will be on the ballot for the first time, insisted that he was not going anywhere before Tuesday’s primaries.

“I’m optimistic,” he told voters in Selma, Alabama, where many of the White House hopefuls gathered for ceremonies commemorating civil rights heroism.

Through four primary contests, the AP allocated at least 58 delegates to Sanders, including two added Sunday as South Carolina’s remaining votes dribbled in. Biden vaulted past Buttigieg into second place with at least 50 delegates — shrinking Sanders’ lead from what had been 30 delegates before South Carolina to eight. Buttigieg, Warren and Klobuchar remained stuck at 26, eight and seven, respectively.

But the first four states were always more about momentum more than math. Super Tuesday states offer a trove of 1,344 new delegates based on how candidates finish. Just 150 delegates have been awarded so far.