Against the backdrop of the Queensbridge Houses, the largest public housing development in the nation, Sanders railed against President Donald Trump, income inequality, racial disparities, status quo politics and the economic elite.

“A few miles away from here, people make unbelievable amounts of money and live in incredible and ostentious luxury,” he said, “while right across the street from us, people are struggling day after day just to survive.”

He also assured the crowd that he is equipped to be president despite his recent health setback.

“I am more than ready to take on the greed and corruption of the corporate elite and their apologists. I am more ready than ever to create a government based on the principles of justice,” Sanders said.

“To put it bluntly," he added, "I am back.”

Ocasio-Cortez, his “special guest,” described Sanders as an iconoclast who has consistently fought for economic and social rights, especially when it was unpopular.

“When I was a child that relied on CHIP so that I could see a doctor, Bernie Sanders fought for a single-payer health care system,” she said. “When the federal government decided to discriminate and abandon my queer family and friends, Bernie Sanders was putting his career on the line for us.”

Ocasio-Cortez said Sanders’ 2016 presidential campaign “fundamentally changed politics,” and that he has pushed Democrats to embrace Medicare for All and reject corporate donations. Her appreciation for Sanders has only grown since she arrived in Congress: “Every trick in the book, psychological and otherwise, is used to get us to abandon the working class.”

Ocasio-Cortez’s endorsement delivered a much-needed jolt to Sanders’ campaign. The Vermont senator had been eclipsed in national and early-state polls by Warren even before his heart attack, and his health scare brought unwanted attention to his age.

Even worse, Warren has cut into his support among young people and liberals, two key voting blocs in his coalition.

But Ocasio-Cortez’s nod has sent the unmistakable message that the battle for the left wing of the Democratic Party is not over. Both Sanders and Warren had been courting Ocasio-Cortez for months, meaning that his gain is indisputably her loss.

“There are few more notable endorsements on the Democratic side than AOC’s,” said Rebecca Katz, a progressive consultant who advised Cynthia Nixon’s left-wing gubernatorial campaign in New York. “This is a real shot in the arm for Bernie and helps energize the base.”

Sanders’ aides believe that Ocasio-Cortez’s endorsement will not only excite his current voters, but also broaden his appeal among young voters, people of color, and women who are not yet behind him. She is expected to campaign for him soon in the first-in-the-nation caucus state of Iowa.

“She has broad approval across the Democratic Party. People really find her very compelling in how she talks about the issues,” Faiz Shakir, Sanders’ campaign manager, told POLITICO. “She extends Bernie Sanders’ argument and reaches many of the same people with her core message, but her background and language may make her able to reach additional people.”

Rep. Ilhan Omar (D-Minn.), another member of the so-called “Squad,” also said this week that she is endorsing him. A third member, Rep. Rashida Tlaib (D-Mich.), is expected to back him soon as well, according to a source familiar with the situation.

Sanders’ advisers said Ocasio-Cortez and Tlaib’s endorsements demonstrate the multiracial working-class movement that he is building.

“They are the symbol of the diversity the senator has always had, but not gotten credit for,” said Nina Turner, Sanders’ campaign co-chair.

Though Ocasio-Cortez’s endorsement certainly prevented a raft of negative headlines that would have been written if he’d lost her support to Warren, political insiders and even some of Sanders’ rallies are skeptical that it will help him pull in new voters.

Jonathan Tasini, the author of "The Essential Bernie Sanders and His Vision for America" and a national surrogate for Sanders in 2016, said the Ocasio-Cortez fans who weren’t already with Sanders “could fit into a booth at the local diner.” Omar’s nod, though, might have more clout, he said.

“I doubt any single endorsement ever changes the nature of a race,” he said. “I’d wager Omar’s support, though less flashy in the media sphere, is more significant if one is thinking, ‘How does this expand Bernie’s voting base?’”

Sanders was off the campaign trail for nearly two weeks before returning to the stump on Tuesday for the Democratic debate. He delivered what was widely considered to be a strong performance in Ohio.

Michael Moore, the liberal filmmaker who backed Sanders in the 2016 primary, also officially endorsed him on Saturday.

“The only heart attack we should be talking about is the one Wall Street is going to have when Bernie Sanders is president,” he said.

Three state senators from New York — Mike Gianaris, Jessica Ramos and Luis Sepulveda — revealed Saturday that they are supporting Sanders as well.

In addition to showing that Sanders can draw a larger crowd than Warren, his team sought to use the rally to draw policy contrasts between the two candidates. His affordable housing and climate change plans, which both go beyond what she has proposed, were focal points of the event.

Even if many of Ocasio-Cortez's supporters were behind Sanders already, this is not a typical politician's endorsement. She has some 5.6 million Twitter followers, a demonstrated knack for creating viral moments — and a level of fame that's almost unheard of for a first-year member of Congress. All of which makes the impact hard to predict.

But that's a question for later. On Saturday in New York, Sanders and his campaign were content to relish the scene.

“It’s a beautiful moment for him, for our campaign, for this movement,” Turner said.