Zohran Mamdani’s growing influence over the Democratic party was on show in New York City on Tuesday as three congressional candidates endorsed by New York’s democratic socialist mayor won closely watched primaries, while voters in Maryland, Utah and South Carolina cast ballots in primaries and runoffs.

Brad Lander, the former New York City comptroller who also ran for mayor last year before endorsing Mamdani, won his race comfortably, defeating the Democratic representative Dan Goldman.

Another Mamdani ally,Claire Valdez, a state lawmaker and former union organizer, defeated Antonio Reynoso, the preferred successor of retiring Democratic Representative Nydia Velázquez in New York’s seventh district, encompassing parts of Brooklyn and Queens. And in a stunning upset, the public defense investigator Darializa Avila Chevalier toppled Representative Adriano Espaillat, the powerful five-term incumbent who chairs the Congressional Hispanic caucus, in the state’s diverse 13th congressional district, which covers Upper Manhattan and parts of the Bronx.

“What a glorious time to be a New Yorker,” Lander declared at this election night party in Brooklyn, where he was joined by the mayor. Mamdani then appeared at a watch party for Valdez, where he told a jubilant crowd: “The old politics that got us into this crisis is not the politics that’s going to get us out of this crisis.”

It was a clean sweep for Mamdani, who waded into the House primaries earlier this year, spending his political capital to boost three leftwing allies – a gamble that would test his popularity and his influence. With his slate of candidates all but certain to be elected to Congress in November, Mamdani has left his stamp on the state’s congressional delegation and expanded his ascendant progressive movement.

Elsewhere in the city,Jack Schlossberg, the grandson of John F Kennedy, was unsuccessful in his bid to revive the political legacy of the US’s most vaunted political family.

In a House race that attracted outsized national attention, Schlossberg, 33, had hoped to parlay his huge social media presence and charisma into a Congressional seat, but he came up short in a crowded field of Democrats hoping to succeed the long-serving representative Jerry Nadler. Micah Lasher, a longtime New York politician and self-described “nerd”, won the primary in New York’s 12th district, a deep-blue district whose voters tend to identify as liberal rather than left-wing. The race also included the prominent anti-Trump critic George Conway and state assembly-member Alex Bores, whose candidacy became the fulcrum for what observers described as an “AI civil war”. Lasher will be the heavy favorite to win the safely Democratic district in the November midterm election.

Late on Tuesday night, Queens-born Donald Trump celebrated the defeat of both Goldman and Conway in a pair of social media posts. “Weak and pathetic Congressman Dan Goldman just lost, BIG! I guess people didn’t like him illegally targeting President TRUMP,” the president said of the congressman, who served as the lead counsel to House Democrats during the Trump’s first impeachment. Of Conway, whose ex-wife was a top adviser to the president during his first term, Trump gleefully predicted that he would “end up at about 5% of the vote in a rather weak field of young and aggressive Communists”.

Though the night highlighted the growing influence of the party’s left flank, moderate Democrats prevailed in a handful of districts that will be consequential in November.

On Long Island, the Democratic freshmen representatives Tom Suozzi and Laura Gillen easily fended off primary challenges as they prepare to defend their swing-district seats in November.

And in a battleground Hudson valley district, Cait Conley, the former White House counter-terrorism official and army combat veteran, won a competitive Democratic primary to take on the Republican representative Mike Lawler. New York’s 17th district is one of just three across the US that voted in 2024 for Kamala Harris for president but elected a Republican member of Congress, and Lawler is considered one of the most endangered members of the House in a year when Democrats hope voters will deliver a strong rebuke to Trump and his unpopular presidency.

“No one is coming to save us,” Conley said in remarks on Tuesday night. “We are the cavalry.”

Still, there were signs Trump’s stranglehold on the Republican party remained intact, as Anthony Constantino won the Republican primary in the upstate New York 21st congressional district. Constantino, who was endorsed by the president, faced Robert Smullen, a state assemblyman who was backed by local party officials.

Constantino will be the favorite to win the November election in a heavily Republican seat vacated by the Maga enthusiast Elise Stefanik. Stefanik, who the president nominated for UN ambassador before withdrawing that nomination, ended her subsequent campaign for New York governor last year.

In Maryland, Adrian Boafo won the extremely crowded primary race to succeed Steny Hoyer, the longest-serving House Democrat and a longtime member of leadership who is retiring at the end of his 23rd term. Boafo, a state delegate, defeatedtheformer US Capitol police officer Harry Dunn, who defended the building on January 6, and businesswoman Quincy Bareebe.

In one of the most expensive House primary races in US history, the Democratic congresswoman April McClain Delaney fended off her predecessor, the former Democratic congressman David Trone, who sought to reclaim his seat in Maryland’s sixth district after an unsuccessful bid for Senate two years ago. In Utah, former congressman Ben McAdams, a political moderate, won the primary to compete in a ​n​ewly drawn Democratic-friendly district in Salt Lake City​.

And in South Carolina, the state attorney general, Alan Wilson, won the runoff for the Republican nomination for governor. Trump initially endorsed the lieutenant governor, Pamela Evette, in the race, but at the last minute decided to endorse both candidates, saying voters “can’t go wrong”.

In the state’s first congressional district, Nancy Lacore, a three-star navy rear-admiral fired by the defense secretary, Pete Hegseth, last year, defeated US Coast Guard veteran Mac Deford in the runoff for the Democratic nomination.