Congresswoman Alexandria Ocasio-Cortez formally endorsed Senator Bernie Sanders' 2020 bid at a massive rally in Queens, New York, on Saturday. Sanders' campaign said more than 25,000 attended the rally, making it the largest rally so far for a Democrat in the 2020 campaign.

Ocasio-Cortez was a 26-year-old organizer for Sanders' unlikely presidential campaign in 2016. A few years later, she's a freshman congresswoman who has rapidly become a progressive star, and Sanders can hardly be considered an underdog in the primary race. One thing, however, has not changed: Ocasio-Cortez's support for Sanders' presidential aspirations.

Saturday's rally intended to showcase Sanders' robust return to campaigning after the 78-year-old suffered a heart attack earlier this month. It is also proof that Ocasio-Cortez believes Sanders' vision is the right one for the country.

Get updates from the campaign trail delivered to your inbox

In her speech endorsing Sanders, Ocasio-Cortez recalled her days working as a bartender, and said that Sanders' progressive policies inspired her to recognize her "inherent value as a human being."

"It wasn't until I heard of a man by the name of Bernie Sanders that I began to question and assert and recognize my inherent value as a human being that deserves health care, housing, education, and a living wage," Ocasio-Cortez said.

Ocasio-Cortez later posted a video on Twitter announcing her endorsement.

Today I am endorsing Senator @BernieSanders for president. In the end, we must come together to defeat Donald Trump. We should do so knowing he is a symptom of a larger problem - and our greatest hope is a multiracial, working class movement in the United States of America. pic.twitter.com/9fiTS7FTX9 — Alexandria Ocasio-Cortez (@AOC) October 19, 2019

Although Sanders has consistently out-raised other candidates — his campaign received over $25 million in the third quarter — he is not considered the frontrunner. His polling numbers have remained consistently high, but has not achieved the kind of momentum seen with Senator Elizabeth Warren.

Warren's numbers have exceeded those of former Vice President Joe Biden in recent polls. Warren and Biden are generally considered co-frontrunners, a position solidified by the Democratic debate on Tuesday.

Warren and Sanders share several policy positions, including Warren's support for Medicare for All, a policy popularized by Sanders in the 2016 campaign. With Ocasio-Cortez's endorsement, Sanders intends to signal to progressives in the Democratic Party that he, not Warren, is the right person to represent the left in the Democratic primary.

Sanders has also been endorsed by Congresswoman Ilhan Omar, another freshman congresswoman and rising progressive star in the Democratic Party.