New York City Mayor Zohran Mamdani’s endorsements led to significant victories for progressive and democratic socialist candidates in Tuesday’s Democratic congressional primaries across the city, shaking up the established political order. The results, which saw Mamdani-backed candidates unseat two incumbents and defeat a handpicked successor, underscore a growing divide within the Democratic Party ahead of the November midterm elections.

In one of the most notable upsets, Darializa Avila Chevalier, a democratic socialist and activist who previously helped organize pro-Palestinian protests at Columbia University, defeated five-term incumbent Rep. Adriano Espaillat, the head of the Congressional Hispanic Caucus. Avila Chevalier, a 32-year-old PhD student with no prior elected experience, faced scrutiny during the campaign over past social media posts calling for the abolition of police and prisons, among other controversial statements, though she apologized on the trail.

Former New York City Comptroller Brad Lander—a progressive ally of Mamdani who, unlike Avila Chevalier and Claire Valdez, is not a member of the Democratic Socialists of America (DSA)—won a primary against two-term Rep. Dan Goldman in the city’s 10th Congressional District. Lander ran on a platform critical of U.S. military aid to Israel, contrasting with Goldman’s support by pro-Israel groups including AIPAC, which became a major point of contention in the race.

Claire Valdez, a state Assembly member and DSA affiliate, secured the nomination to succeed retiring Rep. Nydia Velazquez, defeating Brooklyn Borough President Antonio Reynoso, despite Velazquez’s endorsement of Reynoso. Valdez campaigned on progressive issues such as abolishing U.S. Immigration and Customs Enforcement (ICE) and advocating for Palestinian rights.

While Mamdani endorsed these insurgent candidates, he remained neutral in the primary for New York’s 12th Congressional District, where state Assembly member Micah Lasher won the nomination to succeed retiring Rep. Jerry Nadler. This race drew national attention due to high-profile contenders including Jack Schlossberg, grandson of President John F. Kennedy. Lasher received endorsements from Nadler, Governor Kathy Hochul, and former Mayor Mike Bloomberg, with significant support from AI and technology industry super PACs.

The outcomes highlight a growing tension within the Democratic Party between the progressive, democratic socialist wing, epitomized by Mamdani and his allies, and the more centrist, establishment faction led by figures such as House Minority Leader Hakeem Jeffries. Jeffries, who backed the incumbents, downplayed the impact of the primary results, stating that the overall makeup of the House Democratic caucus would not be substantially altered by these contests.

Beyond New York, primaries in other states reflected similar ideological battles. In Maryland, Adrian Boafo, endorsed by retiring Rep. Steny Hoyer, benefited from substantial spending by crypto and pro-Israel aligned PACs. In Utah’s newly drawn congressional district, former Rep. Ben McAdams prevailed in a Democratic primary supported by more moderate voters over candidates endorsed by progressive leaders such as Sen. Bernie Sanders.

The primaries underscore the challenges facing Democratic leadership as they navigate an increasingly polarized base. The victories of Mamdani’s candidates signal a rise in influence for the democratic socialist wing in urban centers, but also highlight potential difficulties in unifying the party ahead of a crucial midterm election cycle and beyond.