Massachusetts 6th District House Race: Who Will Win

Dr. Mariah Lancaster has withdrawn from the Democratic primary for Massachusetts' open 6th Congressional District and endorsed fellow candidate State Rep. Tram Nguyen. Lancaster, a veterinarian who has also worked at the U.S. State Department and in the U.S. House, announced the decision Saturday on social media, praising Nguyen's "work ethic, backbone, and integrity" and calling her prepared to be a "progressive champion" for the district.

The seat opened after Rep. Seth Moulton said he would challenge Sen. Edward Markey in the 2026 Democratic Senate primary. With Lancaster out, five Democrats remain in the 6th District race. Nguyen has also picked up endorsements from Reps. Ayanna Pressley and Lori Trahan, adding momentum as the field narrows ahead of the primary.

Massachusetts primary voters largely stuck with incumbents while setting up several marquee fall races. Republican Mike Minogue, the former Abiomed executive who self-funded his campaign with roughly $15 million, defeated Brian Shortsleeve by a wide margin to earn the right to challenge Gov. Maura Healey, who ran unopposed. In the U.S. Senate primary, Ed Markey beat back a challenge from Rep. Seth Moulton by a nearly two-to-one margin, adding Moulton to a list of younger rivals, including former Rep. Joe Kennedy III, that Markey has turned aside in recent cycles.

Dan Koh won the crowded Democratic primary for Moulton's open House seat after a previous unsuccessful bid in 2018. All five incumbent U.S. House members facing primary challengers won, though Rep. Richard Neal saw an unexpectedly close race against a first-time candidate. The Norfolk County district attorney's race remains uncalled, with Djuna Elizabeth Perkins holding a narrow lead. On Beacon Hill, Boston Mayor Michelle Wu backed challengers against two state senators who had opposed her property tax proposal.