The mood among Bernie Sanders supporters after Super Tuesday is one of frustration — and devastation. For the second election in a row, they are watching the Democrat establishment maneuver to deny Sanders the nomination.

And this time, Sanders was the presumptive frontrunner. In the spin room after the Nevada debate, there was even talk about potential Cabinet picks in the Sanders administration.

And then, within 72 hours of polls closing in South Carolina, it was all but over. Seasoned political observers agreed that they had never seen anything like it in presidential politics.

Last Wednesday, Sanders told a crowd in Charleston that he was within “single digits” of former Vice President Joe Biden in South Carolina.

That was the day House Majority Whip Rep. James Clyburn (D-SC) endorsed Biden. And on Saturday, the Democratic voters of the Palmetto State marched to the polls and chose Biden — overwhelmingly.

After more than three decades of trying, Biden finally won a presidential primary contest.

That was the signal.

In a breathtaking 24-hour period, Sen. Amy Klobuchar (D-MN) and former South Bend, Indiana, Mayor Pete Buttigieg dropped out of the race and flew to Dallas, Texas, to endorse Biden. So, too, did former Rep. Beto O’Rourke (D-TX).

A slew of former Barack Obama administration officials, notably Susan Rice, suddenly backed Biden as well.

The results were stunning. Not only did Biden win across the South, but he also won Minnesota and Massachusetts and Maine, states in which he barely had a campaign and had been an afterthought in the polls.

Sanders took the biggest prize, California, but Biden won a close race in Texas, where Sanders had predicted victory. By the end of the night on Super Tuesday, Biden was the presumptive nominee and James Carville was telling Sanders to quit.

The Empire had struck back.

The hidden hand behind the scenes was likely former President Obama himself, who called the candidates after the South Carolina primary.

Obama had been reluctant to endorse his former deputy, reportedly concerned — for good reason — about Biden’s weaknesses as a candidate.

But faced with the prospect of Sanders seizing the party, and leading it to “certain death,” the machine lurched into action with brutal efficiency.

Former presidential candidate Marianne Williamson, who had recently endorsed Sanders, called Biden’s victory a “coup.” It was a repeat of the Democratic National Committee effort to rig the primary for Hillary Clinton — the most signifiant revelation that Wikileaks provided in the 2016 election.

The only question is whether Sanders’s supporters will try to fight the party, as they did in 2016, or whether they will unite behind Biden to defeat Trump.

Cenk Uygur of The Young Turks promised that Sanders supporters would fight back, predicting a “civil war” inside the party “like you’ve never seen before.” He also called out the mainstream media for “lying about Biden’s” record.

“Joe Biden did not get arrested with Nelson Mandela!” Uygur exclaimed. “Who makes up a lie like that? … Stolen valor, that’s what Joe Biden is. He’s stolen valor.” He vowed that Sanders would still win the party’s nomination.

“We cannot let Biden win … Biden is not going to beat Trump. Biden is either near-senile, or actually senile,” Uygur said. “And Biden lies nonstop. He’s gonna get caught … His record [is] worse than Hillary Clinton.”

But do other Sanders supporters feel so strongly about that prospect that they would risk party unity once again? And will Sanders lead them into that fight — the “trench warfare” that Uygur said the establishment started first?

In 2016, after losing California unexpectedly, Sanders promised his supporters to take his campaign all the way to the floor of the Democratic National Convention in Philadelphia, Pennsylvania. “The struggle continues!” he said.

In the end, Sanders meekly threw his support to Clinton. But his supporters brought the fight to Philly, disrupting speakers and staging a walkout — #DemExit — in protest against the party’s heavy-handed effort to suppress them.

They warned that nominating Hillary would elect Trump — and they were right.

But would they risk a second term for Trump by rebelling again?

A man outside the Sanders rally in Los Angeles on Sunday evening told Breitbart News that there were plans for “mass demonstrations at the convention” in July in Milwaukee, Wisconsin, and throughout the country, including at party HQ, if the Democrats tried to steal the nomination from Sanders again.

Managing that backlash is now the second-most important task for the Democrat establishment, after making sure Biden beats Sanders in the delegate count.

A confrontation looms between Obama and the Sanders camp, as the one-time “community organizer” faces down the radical left-wing activist masses from whence he rose, and tries to prevent them from doing what he did when he took on the Democratic Party establishment in 2008 — and won.

Do not put it beyond him. If anyone can make the case, it is Obama.

And he may not be alone.

Watch what Rep. Alexandria Ocasio-Cortez (D-NY) does: she has argued Biden cannot win, but she will need party support to mount a Senate challenge in 2022, or (yes) a presidential run in 2024.

If AOC and Obama make the pitch, the “Bernie bros” may fall into line behind Biden.

Or not.

They may lose the primary, but 2020 is still in their hands.

Joel B. Pollak is Senior Editor-at-Large at Breitbart News and the host of Breitbart News Sunday on Sirius XM Patriot on Sunday evenings from 7 p.m. to 10 p.m. ET (4 p.m. to 7 p.m. PT). He earned an A.B. in Social Studies and Environmental Science and Public Policy from Harvard College, and a J.D. from Harvard Law School. He is a winner of the 2018 Robert Novak Journalism Alumni Fellowship. He is also the co-author of How Trump Won: The Inside Story of a Revolution, which is available from Regnery. Follow him on Twitter at @joelpollak.