Former Biden White House aide Dan Koh has won the Democratic primary election for Massachusetts’s 6th Congressional District, emerging victorious from a crowded field of candidates seeking the open U.S. House seat.
Succession for Open Congressional District
The 6th Congressional District seat became open after incumbent Representative Seth Moulton launched a primary challenge against incumbent U.S. Senator Ed Markey. Markey defeated Moulton in the statewide Democratic Senate primary, leaving the U.S. House seat open for a new Democratic nominee.
Koh’s primary victory positions him to contest the district following a high-profile primary race that drew local and regional focus as voters evaluated candidates competing to succeed Moulton.
Background and Primary Contest
Prior to running for the House seat, Koh served as an official in the Biden White House administration. His campaign in the crowded Democratic primary focused on his experience in public administration and government leadership.
Following the September 1, 2026 primary results, Koh advances as the party’s nominee for the general election to represent Massachusetts’s 6th Congressional District in the U.S. House of Representatives.
