Auchincloss defeats progressive Poulos in Massachusetts primary

Incumbent Rep. Jake Auchincloss won the Democratic primary in Massachusetts' 4th district against progressive challenger Jason Poulos, who ran on Medicare for All and ending U.S. military aid to Israel. The result signals continued strength of the party's center-left establishment in a district that includes Newton and Brookline, despite a well-organized left-wing insurgency backed by Bernie Sanders-aligned activists. The outcome may temper progressive momentum in the 2026 midterm cycle.