NEW YORK CITY — Mayor Zohran Mamdani and his allies swept a series of congressional primaries in New York City on Tuesday, ousting two sitting congressmen in a remarkable show of force for the insurgent left that sent shock waves through the Democratic Party.On Tuesday, Adriano Espaillat, who leads the Congressional Hispanic Caucus and is in his fifth term, was defeated by Mamdani’s most polarizing pick, Darializa Avila Chevalier, a democratic socialist who once helped organize pro-Palestinian protests at Columbia University.Another candidate backed by the mayor won an open House seat, and a handful of democratic socialist challengers he supported were winning down the ballot.For months, Mamdani threw himself and his energized political organization into the three marquee congressional contests, campaigning late into the night in the race’s final days and calling the election a referendum on the direction of the party.All the winning candidates share Mamdani’s progressive economic platform, and they each ran campaigns that focused intently on ending American support for Israel, a sign of how far public opinion has shifted on the issue, even in New York.Late Tuesday night, the mayor stood beaming at a victory party in Brooklyn, where supporters chanted “Free, free Palestine” and “D.S.A.” After embracing many of the same advisers who led his own successful campaign last year, he declared “a new chapter in our party’s history.”“A year ago, it was not the end of a political movement,” he said. “It was the beginning.”Dan Goldman, a two-term incumbent, was beaten by the Mamdani-backed former city comptroller Brad Lander, a fixture among New York progressives who has often shown sympathy to the democratic socialist movement.Another Mamdani ally, democratic socialist state Assembly Member Claire Valdez, defeated Brooklyn Borough President Antonio Reynoso, the handpicked successor of retiring US Representative Nydia Velazquez.New York’s primary will determine which challengers the party nominates to run in the midterm elections in November. That vote will, in turn, decide which party controls Congress, giving its lawmakers the power to aid or impede US President Donald Trump’s legislative agenda for his final two years in office.Most congressional districts in New York City are solidly left-wing bastions, meaning the winners of those races are all but assured to skate to victory in November.Tuesday’s primaries represented a major political gamble for the 34-year-old mayor, whose strength is surging, and a potential headache for Democratic leaders, who fear that Mamdani and his loyalists may push the party too far left ahead of midterm elections.The sweep also sends an undeniable message to establishment Democrats in Washington, including House Democratic Leader Hakeem Jeffries, who campaigned against Mamdani’s candidates and lost. Mamdani and his slate were openly fighting for dramatic change on key issues, with Israel’s genocidal war against Palestinians in Gaza and affordability chief among them.Jeffries downplayed the influence of the Mamdani-backed candidates.“We have agreed to strongly disagree,” Jeffries said of Mamdani on Capitol Hill. “There are 215 members of the House Democratic caucus. A handful of primaries that go in one direction or the other, in a given state or two, aren’t going to reshape who we are as House Democrats.”Meanwhile, Democrat Jack Schlossberg, the 33-year-old grandson of former President John F. Kennedy, failed in his bid to write his own chapter in Camelot lore as he competed in a crowded field for a seat being vacated by retiring US Representative Jerry Nadler. Mamdani made no endorsement in that hotly contested race.Establishment Democrats celebrated the victory of state Assembly Member Micah Lasher, a longtime government hand backed by Democratic leaders, who prevailed in a field that also included anti-Trump activist George Conway and Assembly Member Alex Bores, whose proposals to regulate artificial intelligence triggered tech industry blowback.