Brad Lander defeated Representative Dan Goldman in a Democratic primary on June 23, 2026, for a House seat representing parts of Brooklyn and lower Manhattan. What made this race unusual was not just Lander's win — it was that New York City Mayor Zohran Mamdani backed Lander and other candidates who all defeated sitting House members on the same night.

Lander used to be New York's Comptroller, a financial oversight role. He ran against Goldman by criticizing Israel's military actions, a position that mattered in a district with many progressive voters. Goldman had held the seat since 2023. Their disagreement on Israel policy was the race's most defining issue.

Other issues also worked against Goldman. Lander highlighted how immigration enforcement was affecting the district's communities, raising the question of deportations during the campaign. In early June, a fact-checking organization reported that Lander had shared a video that altered a clip of Goldman speaking — something that drew attention in the final weeks.

Two other Mamdani-backed candidates also won that night. Darializa Avila Chevalier defeated Representative Adriano Espaillat, and Claire Valdez ran with Mamdani's support, per NBC News.

Why This Matters

Mayor Mamdani took office in 2025 after winning the city's mayoral primary. He has since built a political operation that works with Democratic Socialists of America groups. Before the June 23 primary, Reuters reported that his endorsed candidates were positioned to win multiple House races.

This is unusual for New York. City mayors typically stay focused on city problems and avoid fights with Congress members, who can affect city funding and policy. Mamdani did the opposite. He used his mayor's organizing resources to run campaigns against sitting House Democrats — something the city hasn't seen at this scale before.

Another Race

In New York's 12th Congressional District, Micah Lasher won the Democratic primary for an open House seat. This seat opened because veteran Representative Jerrold Nadler retired. Jack Schlossberg was among those who ran for the seat, according to the Washington Post and NY1.

What Happens Now

The November general election will almost certainly elect Democrats in both districts. New York's 10th and 12th districts vote Democratic by large margins — which means winning the Democratic primary is the decisive contest. Lander and the other Mamdani-backed winners are virtually certain to win in the fall.

The bigger question is what this means for Democrats in Congress. Goldman had been a visible voice for the party's center-leaning wing. With him and Espaillat out, there are fewer moderate Democrats in New York's delegation. The new members elected with Mamdani's support will likely vote with the party's left wing on spending, military aid conditions, and other major issues.

Mamdani has been mayor for just over a year. He now claims significant credit for reshaping New York's House delegation. Whether this power will last, or whether Goldman and Espaillat were simply weak candidates in districts that had moved left, will become clear as future elections play out.