WASHINGTON — The Democratic empire is quickly aligning its forces to strike back at Bernie Sanders.

First, billionaire Tom Steyer dropped out of the race for the Democratic presidential nomination after former Vice President Joe Biden romped to victory in the South Carolina primary Saturday.

Former South Bend, Indiana, Mayor Pete Buttigieg and Sen. Amy Klobuchar, D-Minn., exited in quick succession Sunday and Monday and were expected to endorse Biden at a rally in Texas on the eve of the Super Tuesday contests that will pick roughly one-third of the delegates to the Democratic convention. Amid the candidate dominoes, a legion of current and former party officials threw their weight behind Biden, who had all but been left for dead by party elites a couple of weeks ago.

"It reflects the urgency of what we’re going into on Super Tuesday," said Adrienne Elrod, a Democratic strategist who worked on Hillary Clinton's bids for the presidency. "That's a big show of force that the left-of-center wing of the Democratic Party is consolidating around Joe because they understand what’s at stake, they understand the urgency, and they don’t want this to be handed to Bernie Sanders on Super Tuesday."

The Vermont senator, who campaigns against the establishment of both parties and raises money by accusing the Democratic Party of conspiring against him, said Monday that he was not surprised by the latest developments.

"The corporate establishment is coming together, the political establishment is coming together, and they will do everything," Sanders told reporters in Salt Lake City on Monday. "They are really getting nervous that working people are standing up."

President Donald Trump — who has looked to stir dissension in the Democratic ranks throughout the primary season — made a similar point Monday, in much stronger terms. "They are staging a coup against Bernie!" he tweeted.

Right now, Sanders leads Biden 60 to 53 in the race for delegates. Buttigieg has 26, Massachusetts Sen. Elizabeth Warren has 8 and Klobuchar has 7. It takes 1,991 to win a majority at the convention, and there are 1,344 delegates in play in 14 states and one territory Tuesday, not including the 13 delegates available in the "Democrats abroad" voting that begins Tuesday and ends a week later.

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Though Biden's big win in the most populous of the first four states to vote put him in shouting distance of Sanders, it is Sanders who is expected to win more delegates on Super Tuesday. Strategists on both sides of the big intraparty divide will make a reassessment of where the race stands after they see what voters actually do Tuesday — and how they may be able to extrapolate the motherlode of data on voting to other states on the primary calendar.

Before Biden's resurgence in South Carolina, party leaders had long worried that fractured support among Biden, Buttigieg, Klobuchar, Warren and billionaire Mike Bloomberg would magnify Sanders' edge on Super Tuesday and put him on a path to winning the nomination outright or making a strong case that he should win with a plurality.

But the departures of Klobuchar and Buttigieg — even after early voting in many states clearly has banked many votes for the two of them — mean Sanders' chances of emerging Tuesday with an eye-popping delegate count are probably reduced.

The likelihood rises that Biden, Warren and Bloomberg will meet the 15 percent threshold necessary to win delegates from statewide and district-level tallies of votes. And while it's hard to predict whether and where the altered field might result in Biden gaining or losing in relation to Sanders, it is more likely that Sanders' raw delegate haul will be lowered and Biden's increased by Klobuchar and Buttigieg removing themselves from the mix.

The truth is, it would have been much more meaningful for them to hit the escape key after neither one won the New Hampshire primary two weeks ago — giving Biden a clear boost — as early voting has been going on in many of the Super Tuesday states for several weeks. Still, Elrod said, it's important that they won't be drawing more votes away from Biden as he tries to make the threshold in states and districts across the country.

If the field had remained intact, she said, "they ran the risk of the left-of-center wing of the Democratic Party coming out of Super Tuesday with very little juice."

Klobuchar framed her decision as "what's best for the country" in a call with her staff, according to an aide who relayed the comments to NBC News. But Klobuchar, 59, and Buttigieg, 38, also had to weigh their narrow hopes of winning the nomination against their desire to remain in good standing with a party establishment anxious to consolidate support behind a single alternative to Sanders.

Before Super Tuesday was the only time Klobuchar and Buttigieg could get out of the race and hope to claim they had put party goals over personal ambition. While that might not matter for candidates who don't plan to run again — at 70 and 78, respectively, it seems less likely that Warren and Bloomberg are thinking about their next bids for the presidency — it would be irresponsible for candidates such as Klobuchar and Buttigieg not to factor their own futures into their thinking.

Both of them could earn consideration as vice presidential picks for a Biden ticket, should he win the nomination.

Klobuchar demurred when NBC's Jane Timm asked her about that possibility in December. But she didn't entirely rule it out, either.

"You don’t see a scenario — you’re all in, no VP interest?" Timm asked.

“I’m going to run and am running for president, and I’m in a good position right now,” Klobuchar said.

Neither Bloomberg nor Warren have shown any signs of leaving the race.

Nomiki Konst, who was a surrogate for Sanders' 2016 campaign, said in a text message exchange with NBC News that the Democratic Party risks alienating many of the voters it will need come November if it picks a nominee by pooling the delegates of a series of candidates behind one rival to Sanders and then turns to a group of party leaders known as superdelegates at the convention in Milwaukee this summer to help nominate Biden.

"If the establishment's entire strategy is dependent on backroom deals with superdelegates, I'm afraid we are in for another four years of Trump and potentially in danger of losing any democratic values left in this country," she said. "I believe the only way we can defeat Trump is by supporting the candidate that has a well-organized, energized, multiracial, multigenerational working-class movement on the ground."

CORRECTION (March 3, 2020, 2:04 p.m. ET): An earlier version of this article misstated the total number of delegates Joe Biden has won. It is 53, not 54.

Jonathan Allen reported from Washington, Ali Vitali from Boston, and Gary Grumbach from Salt Lake City.