Former Democratic presidential primary candidate Pete Buttigieg (right) endorses Joe Biden (left), during an event at the Chicken Scratch restaurant the night before Super Tuesday primary voting, on March 2, 2020 in Dallas. (JUAN FIGUEROA / THE DALLAS MORNING NEWS VIA AP)

DALLAS - Former rivals Pete Buttigieg and Amy Klobuchar endorsed Joe Biden’s presidential candidacy on Monday on the eve of Super Tuesday voting, as moderate Democrats rallied around the former vice president to strengthen his challenge to front-runner Bernie Sanders.

Buttigieg threw his support to Biden at an emotional appearance at a Dallas restaurant, while Klobuchar delivered a barnstorm of a speech at a rally, reminiscent of the types politicians give at their party conventions when anointing their presidential nominees.

“Joe Biden has dedicated his life to fighting for people,” Klobuchar said, before introducing Biden at the rally in Dallas on Monday night.

Not for the rich and powerful, but for the mom, for the farmer, for the dreamer, for the veteran. He can bring our country together 

Pete Buttigieg, the former mayor of South Bend, Indiana

“Not for the rich and powerful, but for the mom, for the farmer, for the dreamer, for the veteran. He can bring our country together.”

Buttigieg, the former mayor of South Bend, Indiana, and the first openly gay presidential candidate, said earlier in Dallas that he was “delighted to endorse and support Joe Biden.”

“He is somebody of such extraordinary grace and kindness and empathy.”

Biden, 77, in turn, told reporters that Buttigieg, 38, “reminds me of my son Beau,” who died in 2015, adding: “To me, it is the highest compliment you can give any man or woman.”

Former US Representative Beto O’Rourke, another former candidate for the Democratic nomination, also endorsed Biden, appearing to cheers as a surprise guest at the rally in Dallas.

For Texas Rep. Beto O'Rourke endorses Democratic presidential candidate former Vice President Joe Biden at a campaign rally on March 2, 2020 in Dallas. (RICHARD W. RODRIGUEZ / AP)

Biden is fresh off a resounding victory in Saturday’s South Carolina primary and is aiming for a strong showing on Super Tuesday against Sanders, a self-described democratic socialist, who many centrist Democrats fear cannot win against Republican President Donald Trump in November.

But Biden still faces a challenge from billionaire former New York Mayor Michael Bloomberg among voters hoping the party will nominate a moderate to face Trump.

Bloomberg, a late entrant to the race, will make his ballot-box debut when 14 states vote on Super Tuesday. He is betting the US$500 million of his own money he has poured into his campaign will allow him to make up for not competing in the first nominating contests in Iowa, New Hampshire, Nevada and South Carolina.

He said on Monday the most likely scenario was that no Democratic candidate would win a majority of delegates and that picking the nominee could come down to “horse trading” at the Democratic convention in Milwaukee in July.

Asked at a Fox News town hall if a contested convention lay in his path to the nomination, Bloomberg said: “That is the way that it would work I would guess.”

The Super Tuesday contests offer the biggest one-day haul of the 1,991 delegates needed to win the party’s nomination at its national convention in July, with about 1,357 delegates, or nearly one-third of the total number, up for grabs.

Fourteen states - California, Texas, Virginia, Massachusetts, Tennessee, Alabama, Arkansas, Oklahoma, Minnesota, Vermont, Colorado, Utah, North Carolina and Maine - as well as American Samoa and Democrats living abroad cast ballots on Tuesday. (The primary for expatriate Americans is scheduled to run through March 10.)

Five candidates - Biden, Bloomberg, Sanders, Senator Elizabeth Warren of Massachusetts and US Representative Tulsi Gabbard of Hawaii - remain in the running for the Democratic nomination, down from more than 20 earlier in the campaign.

Bloomberg and Biden have emerged as the main contenders for the votes of moderate Democrats, while Sanders, a senator from Vermont, is the progressive front-runner nationally, eclipsing Warren.

At a rally on Klobuchar’s home turf in Minnesota on Monday night, he was gracious to his former rivals who endorsed Biden, praising Klobuchar as a hard worker and calling Buttigieg’s candidacy historic.

“Tonight I want to open the door to Amy’s supporters, to Pete’s supporters,” Sanders said. “I know there are political differences but I also know that virtually all of Amy’s supporters and Pete’s supporters understand that we have got to move towards a government that believes in justice and not greed.”

BIDEN’S MOMENTUM

Biden’s high-stakes triumph in South Carolina, where his campaign had said his popularity with black voters would propel him to victory after early disappointing finishes in Iowa and New Hampshire, helped winnow the field.

Billionaire environmental activist Tom Steyer also gave up his campaign on Saturday after a third-place finish in the Southern state in which he had invested most heavily.

ALSO READ: Biden wins South Carolina, aims for Super Tuesday momentum

Sanders’ momentum might not be easily slowed. On Monday, his campaign played down the efforts by moderates to present a united front.

“The establishment is nervous, not because we can’t beat Trump, but because we will,” said Sanders’ campaign manager, Faiz Shakir. “And when we do, the Democratic Party will again be a party of the working class.”

It was not immediately clear who would immediately benefit from the departures of Buttigieg and Klobuchar. A Morning Consult poll taken Feb 23 to 27, for example, before Buttigieg exited the race, showed that 21 percent of his supporters named Sanders as their second choice, 19 percent picked Biden, another 19 percent chose Warren and 17 percent favored Bloomberg.

Biden still lags his rivals in spending and organization in Super Tuesday states and beyond, but his campaign said on Sunday it had raised more than US$10 million over the preceding two days.

Endorsements of the former vice president from elected officials and community leaders poured in on Monday.

READ MORE: Democratic rivals warn Sanders nomination would be 'catastrophe'

Backing from Ohio Democrats including Representative Marcia Fudge and former Cincinnati Mayor Mark Mallory added to endorsements from Senator Tim Kaine and state House of Delegates Majority Leader Charniele Herring of Virginia.

In Colorado, Denver Mayor Michael Hancock has backed Biden. In California, Representative Gil Cisneros is supporting the former vice president.