The June 24 Democratic primaries in New York City saw victories for Darializa Avila Chevalier, Claire Valdez and Brad Lander — all endorsed by Mayor Zohran Mamdani and the Democratic Socialists of America. In two contests, they unseated incumbent Democrats, prompting celebration on the party’s left and alarm among its centrist wing. According to party operatives in Washington, the wins have intensified an internal struggle over the Democrats’ direction ahead of the 2026 midterm elections.

Mamdani, who took office in January after running on a platform of rent freezes, fare-free buses and universal child care, told ABC News that his candidates’ success reflected “a hunger … for a new kind of politics that puts working people at the heart of it.” He welcomed Republican efforts to turn him into the party’s “poster child,” arguing his policies had already proved popular beyond leftist enclaves. Viewed from European capitals, his democratic socialism echoes a broader transatlantic trend of politicians redefining the left around economic redistribution and state-funded services.

But within the Democratic Party, moderate lawmakers and union officials have countered that the movement’s appeal is limited to safe blue districts and risks alienating mainstream voters. Sen. Richard Blumenthal, D-Conn., dismissed the results as “really irrelevant by the time of the elections in November.” Leaders of New York’s Steamfitters Local 638, a historically Democratic-aligned building-trades union, described the DSA-backed candidates as “communists” who do not represent workers like their members and warned of a labour exodus toward Republicans. Meanwhile, Senate colleagues such as John Fetterman (D-Pa.) have publicly warned that Mamdani’s pledge to defy a recent Supreme Court ruling on immigration could precipitate a “constitutional crisis,” amplifying unease among congressional moderates.

Analysts in London and Washington note that Mamdani’s ascent mirrors a pattern in which left-wing primary challengers, energised by discontent over living costs and foreign policy — particularly the war in Gaza — are eroding the institutional hold of party establishments. Six additional left-wing candidates are in races to unseat Democratic incumbents, raising the prospect of the largest progressive bloc in Congress in decades. Moderate House members have told Axios they are bracing for “a war” and may form a counter-bloc to resist legislative demands from new socialist members. The next test will come in November’s general election, when the Mamdani-backed candidates are heavily favoured in their districts, while attention shifts to battleground states like Michigan, where a similar dynamic could reshape the party’s internal calculus.