In a stunning defeat, New York Rep. Joe Crowley, the fourth-most powerful Democrat in the House of Representatives, lost a Tuesday primary to Democratic Socialists of America-backed challenger Alexandria Ocasio-Cortez.

The Washington Post and Associated Press called the race for Ocasio-Cortez at 10:00 PM. The 28-year-old Bronx-born community organizer earned 57 percent of the vote compared to 42 for her veteran lawmaker opponent, with 91 percent of the vote counted.

“I want nothing but the best for Ms. Ocasio-Cortez. I want her to be victorious,” Crowley said in conceding the race, according to the AP.

Ocasio-Cortez was the first primary challenger in 14 years for Crowley, who until Tuesday was seen as a possible successor to House Speaker Nancy Pelosi (D-CA). Her victory marks a dramatic end to to a feisty primary campaign that drew national attention thanks to Ocasio-Cortez’s boldly progressive platform. She campaigned on abolishing the Immigration and Customs Enforcement agency and on Medicare for All.

The NY-14 congressional seat covers the east Bronx and several neighborhoods in north-central Queens. It is seen as safely Democratic, and Crowley was viewed as the clear favorite. He pulled in $3 million this year, has served in Congress since 1999, and was backed by New York’s Democratic establishment.

Ocasio-Cortez made a convincing case that this didn’t—and shouldn’t—matter, proclaiming, in a campaign ad that went viral, “This race is about people versus money. We’ve got people. They’ve got money.”

The young former organizer for the Bernie Sanders campaign won acclaim on the left for her unflinching advocacy for a new vision for the Democratic Party. Ocasio-Cortez rejected corporate donations and was one of the first to call for doing away with ICE—a position that has since gained popularity among a small but growing number of other Democratic candidates, as well as some lawmakers already in Congress.

Another Democratic New York incumbent facing a more progressive challenger on Tuesday was also in a tight race. Rep. Yvette Clarke had pulled in 51 percent of the vote with 93 percent of votes counted in her central Brooklyn district as of 10: 43 PM, compared to 48.8 for opponent Adem Bunkeddeko.