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Stunning upset: 28-year-old Alexandria Ocasio-Cortez defeats Rep. Joe Crowley in New York primary.

Joe Crowley has been in Congress since 1999. But in a shocking result, he has now lost Tuesday night’s Democratic party for New York’s 14th Congressional District—to Alexandria Ocasio-Cortez, a 28-year-old native of The Bronx. (Crowley previously represented New York’s 7th District.)

Crowley had been ready to replace Representative Nancy Pelosi as the next House Democratic leader, but Ocasio-Cortez defeated him 57 to 42, as of 10 pm on Tuesday. This is more than a victory: It’s an upset, and it’s the clearest sign yet that a surging leftist faction is reshaping the Democratic Party.

Ocasio-Cortez, a former organizer for Senator Bernie Sanders’s presidential campaign, ran openly on Medicare for All, free higher education, and abolishing ICE. She is a socialist, and belongs to Democratic Socialists of America, which experienced significant growth as the Sanders campaign gained prominence. She articulated her political views in a June 22 interview with The Nation:

Ocasio-Cortez characterizes narratives that pit race against class as a “fundamental misunderstanding” of how our country works: “I can’t name a single issue with roots in race that doesn’t have economic implications, and I cannot think of a single economic issue that doesn’t have racial implications. The idea that we have to separate them out and choose one is a con.”

The 14th is a deep blue district, meaning Ocasio-Cortez is nearly guaranteed to win her general election in November. Less than two full years after working on the Sanders campaign, Ocasio-Cortez will in all likelihood follow him into Congress. If she does, she’ll become the youngest sitting member of Congress, its second self-identified socialist–and proof that socialist policies don’t necessarily doom political campaigns.