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The establishment wing of the Democratic Party is reeling in the wake of the stunning democratic socialist victories in New York City this week, as races won by progressive challengers exposed different facets of the establishment’s increasingly tenuous hold on its voters.

And the drama is not over yet: The next test of democratic socialism’s appeal will come on June 30, when newcomer Melat Kiros, who has the support of Democratic Socialists of America (DSA) and Justice Democrats, faces off against Diana DeGette in Colorado’s 1st congressional district.

This week in New York City, all three candidates who defeated Democratic Party establishment candidates had a political brand in common: They were progressive insurgents who ran in opposition to Israel’s genocide in Gaza, and all three were endorsed by New York City Mayor Zohran Mamdani. Two — Claire Valdez and Darializa Avila Chevalier — were endorsed by the New York City Democratic Socialists of America (NYC-DSA).

For the NYC-DSA, these results are a continuation of the momentum the organization has built since Mamdani surged to win the mayoral primary last year. “Because of Zohran and NYC-DSA’s success in 2025 and continued success governing the city, we can clearly make the case to voters that being represented by a democratic socialist means their life will change for the better,” NYC-DSA co-chair Grace Mausser told Truthout. Each candidate made Mamdani’s endorsement, and campaign stops with him, a core part of their pitch to voters.

In New York’s 10th congressional district, which covers parts of lower Manhattan and some of Brooklyn’s wealthiest neighborhoods, former city comptroller Brad Lander easily dispatched incumbent Dan Goldman. Meanwhile, in New York’s 7th district, Valdez triumphed over Brooklyn borough president Antonio Reynoso by a margin that topped even the most optimistic polling for her in the days leading up to the election. And, in the showstopper of the night, Avila Chevalier, a political newcomer, defeated Rep. Adriano Espaillat, a longtime congressional representative and the powerful head of the Congressional Hispanic Caucus.

Further down the ballot, the winning streak continued for democratic socialist and progressive candidates.

Further down the ballot, the winning streak continued for democratic socialist and progressive candidates.

Further down the ballot, the winning streak continued for democratic socialist and progressive candidates. Ten DSA-backed candidates won their races for state assembly and senate seats in New York City districts, while another two democratic socialists, Adam Bojak and Jo Bennett, won state elections in Buffalo and Syracuse.

Conrad Blackburn, who was endorsed by the DSA but not Mamdani, lost a primary for the state assembly, as super PACs spent more in this contest than in any New York City race to defeat a DSA candidate.

Mamdani Allies Defeat Establishment Democrats in NYC Congressional Primaries

The political implications for the Democratic Party’s establishment wing are dire. In three congressional primaries, voters spurned candidates who, in prior cycles, would have been seen as shoo-ins to win their elections. The results on June 23 were tantamount to a rejection not just of the individual candidates backed by the party establishment, but of the entire politics that they represented.

Brad Lander Wins After Criticizing Israel’s Genocide in Gaza

Lander ran in a district where he had deep roots and leveraged the visibility he gained during New York’s mayoral primary last year to crush Goldman by more than 30 points. Lander became well known in the mayoral primary for his cross-endorsement of Mamdani at a time when the future mayor was being falsely smeared........

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