Maybe it depends on where you’re standing, but when the results came in for the Democratic primary in New York’s 14th Congressional District, I could feel the earth move—and I’m writing this from London. Alexandria Ocasio-Cortez, a 28-year-old novice who was still working as a bartender just a year ago, waged a brilliant guerrilla campaign against the fourth-ranking Democrat in the house, Joseph Crowley, a 10-term incumbent who outspent her by more than 10-1. Focusing on economic justice, Medicare for All, and the abolition of US Immigrations and Customs Enforcement (ICE), Ocasio-Cortez spent the final weekend of the campaign not ringing doorbells in her district but instead confronting ICE agents at a detention center on the Texas border. Her stunning upset over Crowley—a man widely touted as a possible successor to Nancy Pelosi—inevitably draws comparisons with House majority leader Eric Cantor’s June 2014 defeat by Tea Party candidate Dave Brat.

Like Ben Jealous, the former NAACP president who just won the Democratic nomination for governor of Maryland, Ocasio-Cortez won not only by running unabashedly to the left—both candidates worked for Bernie Sanders in 2016 and were themselves endorsed by Our Revolution—but as a “movement” progressive. It was only last Sunday that The New York Times reassured nervous readers “Bernie Sanders Is Winning Converts. But Primary Victories Remain Elusive.” Not any more. (And not before, either, if you happened to be paying attention to Jess King, Summer Lee, and Sara Innammorato’s wins in Pennsylvania last month.)

Ocasio-Cortez’s victory in particular ought to keep corporate Democrats and their K-street backers awake at night. Because if Joe Crowley isn’t safe when confronted by the right challenger and right message, then nobody is.

Yet amid the celebrations, and despite Ocasio-Cortez’s now being the favorite in the November election, her victory also poses some tough questions for the left—and particularly for those who claim to be leaders in the movement. Unlike Jealous, whose campaign was boosted by appearances by Sanders, Cory Booker, and Kamala Harris—“I have a lot of friends who could be running for president in 2020,” Jealous told the Times—or her opponent, who was backed by such normally progressive unions as the Communications Workers of America, DC 37, and the Amalgamated Transit Union, Ocasio-Cortez got only lip service. Sanders endorsed her, but didn’t campaign for her. The Democratic Socialists of America backed her. But Keith Ellison, Pramila Jayapal, Elizabeth Warren, and other supposed progressive standard-bearers couldn’t be bothered. California Democrat Ro Khanna did endorse her—and her opponent! Even the Working Families Party backed Crowley, though, to his credit, Bill Lipton, the WFP’s state director, admitted, “We didn’t think this one was possible. But the old rules about what’s possible have been proven wrong, and we’re delighted.” Cynthia Nixon and Zephyr Teachout were Ocasio-Cortez’s highest-profile local supporters.

Her victory should encourage both of them—and add a few more worry lines to Andrew Cuomo’s forehead. Much credit also goes to Justice Democrats and Brand New Congress, who recruited Ocasio-Cortez and believed in her long before anyone else thought she had a chance. (Corbin Trent, the co-director of Justice Democrats who also served as Ocasio-Cortez’s communications director, spent weeks trying—mostly without success—to interest reporters in the campaign.) But if the movement is going to become a powerful electoral force—as opposed to an every-four-years guilty bystander—its leaders need to start taking seriously, and acting on, the Sanders campaign slogan: “Not Me, Us.” And that very much includes Bernie Sanders.