White House hopeful Bernie Sanders fired up exuberant supporters at a packed Manhattan rally Wednesday night, promising free college education to a predominantly youthful crowd, and taking verbal jabs at his Democratic opponent, Hillary Clinton.

The U.S. senator from Vermont — trailing Clinton in the polls and in pledged delegates — took the stage at historic Washington Square Park just after 8 p.m. on a cool chilly spring night.

With two iconic Manhattan images lit up behind him — the park’s historic arch and, two-dozen blocks up Fifth Avenue, the Empire State Building — Sanders urged his cheering supporters to band together and upend the status quo.

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“This campaign is about your presence here tonight,” Sanders told the crowd, laced with bundled up millennials, many holding campaign signs in the jammed-pack park. “It is not just about electing a president. It is about creating a political revolution.”

The line is standard boilerplate in his stump speech, but it sent a jolt through the estimated crowd of about 27,000 supporters, many of them squeezed out of the park and instead watched and cheered from surrounding streets.

Sanders predicted victory over Clinton in Tuesday’s New York primary, citing momentum after a string of recent primary victories and polls showing him gaining on or even leading the former secretary of state and first lady.

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He also touted his support of labor unions and their backing of him in return. Earlier in the day, Sanders visited a Communications Workers of America picket line in downtown Brooklyn where Verizon workers were part of a nationwide strike started Wednesday.

“You have chosen to stand up for dignity, for justice and to take on an enormously powerful special interest,” he told the pickets.

Many of the workers later attended the evening speech where Sanders mentioned the labor stoppage.

Leading up to the 74-year-old candidate’s appearance, the campaign rally felt more like a music festival than a campaign rally.

Brooklyn-based Vampire Weekend belted out their hits and a parade of supporters — among them celebrities like actors Tim Robbins, Rosario Dawson and director Spike Lee, bounded to the stage to heap praise on the white-haired candidate.

A sea of Sanders supporters stared back as the speakers urged the crowd to ignore mainline critics who have said a vote for Sanders over Clinton is a wasted vote.

“The establishment has already counted you out before you go to the polls,” civil rights activist Linda Sarsour told the crowd from the stage to boos, not of derision, but agreement.

In the crowd, a group of college students from NYU, which edges up against three borders of the Greenwich Village park, watched and cheered.

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It was the fifth Sanders rally for Oscar Salazar, 20, an NYU student from Westchester County who wore a shirt covered with several images of the candidate’s face. He pointed toward the glowing arch and saw it as a symbol of what he says Sanders represents to him.

“That sends a powerful message, Salazar said of the arch, with a mix of flashing NYPD squad car lights and the length of a bustling Fifth Avenue behind it. “It’s like the doorway to change for voters.”

Leah Gindes, 60, of Hudson Valley, waved a “Boomers for Bernie” sign. She said it is “just not the case” that Sanders’ backers are all young. What she referred to as the 99 percent spans all age groups, she said.

Sanders, clad in a dark-colored windbreaker-style jacket, made it a point in his speech to recognize the Transport Workers Union Local 100, which earlier in the day endorsed him.

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“It is the trade unions of today that are the last lines of defense against a vicious corporate agenda that is working hard to destroy the middle class,” Sanders said, surrounded by members waving signs with the now familiar campaign phrase, “Feel the Bern.”

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TWU Local 100 has 42,000 members.

“We are blue-collar New York,” Local 100 president John Samuelsen said, calling Sanders a “true champion for our cause.”

Sanders also notched his first endorsement from a fellow member of Congress in the form of an NY Times opinion column Wednesday by U.S. Sen. Jeff Merkley (D-Ore.).

Merkley wrote that Sanders is a “determined leader in taking on the concentration of campaign cash from the mega-wealthy that is corrupting the vision of opportunity embedded in our Constitution.”