Alexandria Ocasio-Cortez, the New York Democrat who was elected as the youngest women to serve in congress during the 2018 midterms, has endorsed Bernie Sanders to become the next president of the United States.

Speaking at a rally in Queens, the congresswoman celebrated Mr Sanders’ lifelong career in public service and progressive track record as a Vermont senator.

“We right now have one of the best Democratic presidential primary fields in a generation and much of that is because of Bernie Sanders,” she said.

The congresswoman hailed Mr Sanders' “enormous, consistent and nonstop advocacy” in the Senate, saying: “The halls of congress are no joke. It is no joke to stand up to corporate power and established interest.”

A former volunteer for Mr Sanders’ 2016 presidential bid, the 30-year-old has quickly gained prominence in the US House of Representatives as one of the most outspoken and influential freshmen politicians on Capitol Hill.

Mr Sanders took the stage after Ms Ocasio-Cortez spoke, lifting their hands together before he thanked the more than 20,000 attendees.

“What our campaign is about is not just defeating the most dangerous president in history,” he said. “It is about creating an economy that works for all of us, not just the 1 per cent.”

He added: “I am happy to report to you that I am more than ready, more ready than ever, to carry on with you the epic struggle that we face today. I am more than ready to assume the office of president of the United States. I am more than ready to take on the greed and corruption of the corporate elite and their apologists.”

The rally marked Mr Sanders’ return to the campaign trail after suffering a heart attack earlier this month. He banked on the event as a way to “reassure the American people” he was fit to be the commander-in-chief during a conversation on age at the latest Democratic presidential primary debate – the largest in American history.

Speaking to The Independent in the sunny Queensbridge Park that overlooks the Manhattan skyline, supporters of Mr Sanders said they were excited for his return to the campaign trail.

The Democrat challengers to Trump in 2020 Show all 25 1 /25 The Democrat challengers to Trump in 2020 The Democrat challengers to Trump in 2020 Bernie Sanders The Vermont senator has launched a second bid for president after losing out to Hilary Clinton in the 2016 Democratic primaries. He is running on a similar platform of democratic socialist reform Getty The Democrat challengers to Trump in 2020 Joe Biden The former vice president recently faced scrutiny for inappropriate touching of women, but was thought to deal with the criticism well and has since maintained a front runner status in national polling EPA The Democrat challengers to Trump in 2020 Elizabeth Warren The Massachusetts senator is a progressive Democrat, and a major supporter of regulating Wall Street Reuters The Democrat challengers to Trump in 2020 Amy Klobuchar Klobuchar is a Minnesota senator who earned praise for her contribution to the Brett Kavanaugh hearings Getty The Democrat challengers to Trump in 2020 Michael Bloomberg Michael Bloomberg, a late addition to the 2020 race, announced his candidacy after months of speculation in November. He has launched a massive ad-buying campaign and issued an apology for the controversial "stop and frisk" programme that adversely impacted minority communities in New York City when he was mayor Getty Images The Democrat challengers to Trump in 2020 Tulsi Gabbard The Hawaii congresswoman announced her candidacy in January, but has faced tough questions on her past comments on LGBT+ rights and her stance on Syrian President Bashar al-Assad Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Pete Buttigieg The centrist Indiana mayor and war veteran would be the first openly LGBT+ president in American history Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Deval Patrick The former Massachusetts governor launched a late 2020 candidacy and received very little reception. With just a few short months until the first voters flock to the polls, the former governor is running as a centrist and believes he can unite the party's various voting blocs AFP/Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Beto O'Rourke The former Texas congressman formally launched his bid for the presidency in March. He ran on a progressive platform, stating that the US is driven by "gross differences in opportunity and outcome" AP The Democrat challengers to Trump in 2020 DROPPED OUT: Kamala Harris The former California attorney general was introduced to the national stage during Jeff Sessions’ testimony. She has endorsed Medicare-for-all and proposed a major tax-credit for the middle class AFP/Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Bill De Blasio The New York mayor announced his bid on 16 May 2019. He emerged in 2013 as a leading voice in the left wing of his party but struggled to build a national profile and has suffered a number of political setbacks in his time as mayor AFP/Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Steve Bullock The Montana governor announced his bid on 14 May. He stated "We need to defeat Donald Trump in 2020 and defeat the corrupt system that lets campaign money drown out the people's voice, so we can finally make good on the promise of a fair shot for everyone." He also highlighted the fact that he won the governor's seat in a red [Republican] state Reuters The Democrat challengers to Trump in 2020 DROPPED OUT: Cory Booker The New Jersey Senator has focused on restoring kindness and civility in American politics throughout his campaign, though he has failed to secure the same level of support and fundraising as several other senators running for the White House in 2020 Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Wayne Messam Mayor of the city of Miramar in the Miami metropolitan area, Wayne Messam said he intended to run on a progressive platform against the "broken" federal government. He favours gun regulations and was a signatory to a letter from some 400 mayors condemning President Trump's withdrawal from the Paris Climate Accord Vice News The Democrat challengers to Trump in 2020 DROPPED OUT: Kirsten Gillibrand The New York Senator formally announced her presidential bid in January, saying that “healthcare should be a right, not a privilege” Getty The Democrat challengers to Trump in 2020 DROPPED OUT: John Delaney The Maryland congressman was the first to launch his bid for presidency, making the announcement in 2017 AP The Democrat challengers to Trump in 2020 DROPPED OUT: Andrew Yang The entrepreneur announced his presidential candidacy by pledging that he would introduce a universal basic income of $1,000 a month to every American over the age of 18 Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Julian Castro The former San Antonio mayor announced his candidacy in January and said that his running has a “special meaning” for the Latino community in the US Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Marianne Williamson The author and spiritual adviser has announced her intention to run for president. She had previously run for congress as an independent in 2014 but was unsuccessful Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Eric Swalwell One of the younger candidates, Swalwell has served on multiple committees in the House of Representatives. He intended to make gun control central to his campaign but dropped out after his team said it was clear there was no path to victory Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Seth Moulton A Massachusetts congressman, Moulton is a former US soldier who is best known for trying to stop Nancy Pelosi from becoming speaker of the house. He dropped out of the race after not polling well in key states Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Jay Inslee Inslee has been governor of Washington since 2013. His bid was centred around climate change AFP/Getty The Democrat challengers to Trump in 2020 DROPPED OUT: John Hickenlooper The former governor of Colorado aimed to sell himself as an effective leader who was open to compromise, but failed to make a splash on the national stage Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Tim Ryan Ohio representative Tim Ryan ran on a campaign that hinged on his working class roots, though his messaging did not appear to resonate with voters Getty The Democrat challengers to Trump in 2020 DROPPED OUT: Tom Steyer Democratic presidential hopeful billionaire and philanthropist Tom Steyer is a longtime Democratic donor AFP/Getty

“It was a lot of the same things he’s been saying for a really long time, which is just an ode to his consistency,” said Mary Zaradich from New York. “His voting record is something that I think makes everything he says so much more real and so whenever I hear him speaking I know he’s saying for a fact something that he actually believes in.”

Tiffany Otegbade said Mr Sanders’ speech was “unique” in that the senator is capable of “touching on every single problem in America” by focusing on how interconnected numerous challenges are nationwide.

The New Yorker also said she wouldn’t be concerned voting for him after his heart attack, adding: “People suffer from health problems at any age, so I’m not concerned about that at all.”

Thousands had gathered at the park for the day to hear Mr Sanders deliver his first major speech since he paused his campaign to rest after suffering the heart attack. His wife, Jane Sanders, was the first to take the stage.

“I’m here to tell you Bernie’s back!” she said to cheers.

Filmmaker and activist Michael Moore also spoke at the rally and said the country would benefit from the “wisdom” of having an older president.

He added: “The only heart attack we should be talking about is the one Wall Street is going to have when Bernie becomes the president of the United States!”

The crowd, which spanned the entire park and spilled into the surrounding streets, was riled up throughout the day. Folks chanted everything from “Bernie will win!” to “black lives matter” and “Green New Deal” in bursts as speakers delivered their speeches.

Lauren Puncrots from New York said she had been a supporter of Mr Sanders since 2016 and that she was “not at all” concerned about Mr Sanders’ health.

“Anyone can have a heart attack,” she said. “My great-grandpa dropped dead of a heart attack at 40. Doesn’t matter. [Mr Sanders] is in great shape.”

Mr Sanders, who would be the oldest president elected to the White House, has raked in recent endorsement from young progressives, including Ilhan Omar, a Minnesota Democrat.

Ms Omar and Ms Ocasio-Cortez have both become lightning rods for the right — in a way that is not dissimilar to Mr Sanders’ own trajectory in Washington — as some of the only women of colour to serve in Congress.

They affectionately call themselves members of “the squad,” which also consists of Michigan Democrat Rashida Tlaib and Massachusetts Democrat Ayanna Pressley, two other women of colour elected in 2018.

Though Ms Tlaib was reportedly expected to endorse Mr Sanders, neither she nor Ms Pressley have announced their 2020 endorsements.

It appears Ms Ocasio-Cortez is all in, however, as Mr Sanders said on Saturday he was “looking forward to travelling with all over the country”.

“I don’t know that a congresswoman from New York, one from Minnesota, one from Michigan are super influential to voters in Iowa, New Hampshire, Nevada and South Carolina,” Jess Morales Rocketto, a Democratic strategist who worked on Hillary Clinton’s 2016 campaign, told The New York Times.

She had previously said she was not planning on endorsing any of the nearly 24 candidates who threw their hat in the ring for the Democratic primaries, but reportedly changed her mind following Mr Sanders’ heart attack.

“Her reaction was that this is ... when he needs an injection of energy in the campaign,” a source close to the congresswoman told Business Insider. “She thought: ‘If I have any capacity to do that, I should try.”

Ms Ocasio-Cortez reportedly debated for months over whether to endorse Mr Sanders, whose national organisation Our Revolution endorsed her candidacy against Democratic incumbent Joe Crowley in the 2018 New York primaries, or Elizabeth Warren, the Massachusetts Democrat who has steadily risen in the polls.

Ms Warren has surpassed Mr Sanders in most national surveys to become either the second-place candidate to former vice president Joe Biden or even frontrunner in some polls. Mr Sanders has meanwhile slipped in some surveys over recent months, as the two have fought for the party’s progressive voters.

On Saturday, Mr Sanders thanked his supporters “for their prayers, and their well wishes, and their love”.

He went on to say he would win the presidency and fight for the working class, vowing to double the number of American workers in unions, cancel student loan debt, end “environmental racism” and only nominate Supreme Court justices who support women’s reproductive rights.