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Pete Buttigieg is endorsing former Vice President Joe Biden for president on Monday, a day after the former mayor of South Bend, Indiana, exited the 2020 race.

The endorsement — which came shortly after news broke that Minnesota Sen. Amy Klobuchar would also drop out and endorse Biden — appears aimed at consolidating the moderate Democratic vote behind Biden ahead of Super Tuesday. Biden, who will address supporters in Dallas Monday night, has also won the endorsement of longtime political titans such as former Senate Majority Leader Harry Reid and South Carolina Rep. Jim Clyburn.

Former Texas congressman and presidential candidate Beto O’Rourke will endorse Biden in Dallas as well, two sources familiar with his plans tell NBC News.

Former New York City Mayor Mike Bloomberg meanwhile told reporters on Monday that he is "in it to win it."

Biden, Buttigieg and Klobuchar all ran as moderates with similar health care proposals that departed dramatically from the "Medicare for All" policy offered by progressive front-runner Bernie Sanders.

Sanders told reporters on Monday that "the political establishment is coming together" to try and stop him.

"The corporate establishment is coming together," he said. "The political establishment is coming together and they will do everything. They are really getting nervous that working people are standing up. And by the way, when we talk about South."

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Biden on Monday suggested he would give Buttigieg a spot in his administration if he were to win the presidency. He told NBC News that he spoke to the former mayor on the phone about his exit and "warned him that if I get elected, I'm coming for him."

Trump told reporters on the White House lawn that the Democratic primary "is rigged against Bernie" but that "it was rigged against me and I pulled through." He also suggested that Buttigieg and Klobuchar were endorsing Biden in return for positions in a possible Biden administration. "That's called a quid pro quo, right?"

Buttigieg, an Afghanistan war veteran who was seeking to become the first openly gay nominee of a major political party, won an impressive victory in Iowa and narrowly lost New Hampshire, two overwhelmingly white states.

But his momentum dissolved when the campaign moved to more diverse states. He placed third in Nevada and fourth in South Carolina, faring poorly with Latino and black voters who make up a large share of coming Super Tuesday states.

At a Sunday evening rally in South Bend, Indiana, the city he led as mayor until this year, Buttigieg said that he no longer saw a path to victory and that he had a responsibility to "consider the effect of remaining in this race any longer."

An aide to Biden and an aide to Buttigieg told NBC earlier Monday that the two men had connected with one another by phone. They had attempted to get in touch with one another on Sunday, according to a Buttigieg aide, to talk about consolidating support behind Biden.

Despite the endorsement, it isn’t entirely clear whom Buttigieg's supporters will now back. Recent polling by Morning Consult found his backers divided over their second choices: 21 percent picked Bernie Sanders, 19 percent picked Joe Biden, 19 percent liked Elizabeth Warren and 17 percent were on board with Mike Bloomberg.

Klobuchar, for her part, will fly to Dallas later on Monday to endorse Biden at a rally. It wasn’t immediately clear whether Buttigieg would also make public his endorsement at that rally.

Buttigieg ended his campaign having won 26 delegates; Klobuchar won seven.

What happens now to those delegates is sure to be a big question moving forward.

According to the Democratic National Committee, district-level delegates (those won at the congressional-district level) remain entitled to those former candidates, regardless of their status. However, typically, these ex-candidates release their delegates to vote their choice or encourage them to support the candidate they've endorsed.

The statewide pledged delegates (those won at the statewide level) are reallocated proportionately to the candidates who remain in the race.

However, all pledged delegates are actually not legally bound to their candidates, whether these candidates remain in the race or not. As a result, Buttigieg’s and Klobuchar’s delegates can technically act as free agents.