Dan Koh holds a commanding lead in the Massachusetts 6th Congressional District Democratic primary, scheduled for September 1, 2026, reflecting strong early organization, first-mover ballot qualification with certified signatures, and recent local endorsements such as that from Swampscott Select Board Chair Katie Phelan. The open seat, created after incumbent Seth Moulton entered the U.S. Senate primary, features a crowded field of over a dozen candidates including state Representative Tram Nguyen, who led some March 2026 polls but has seen her support consolidate less effectively amid high undecided rates in later surveys. Fundraising differentials, name recognition from Koh’s prior White House role, and the district’s North Shore and Merrimack Valley voter base have positioned Koh as the consensus frontrunner among traders, while lower-probability contenders trail due to limited visibility and resources in the remaining campaign window.