Dan Koh holds a commanding lead in trader consensus for the Massachusetts 6th Congressional District Democratic primary on September 1, 2026, reflecting his substantial fundraising edge of nearly $4 million, early ballot qualification through signature collection, and former President Biden’s endorsement in early May. The open seat, created by Rep. Seth Moulton’s Senate bid, features a crowded field including state Rep. Tram Nguyen, who topped an early March internal poll before later developments shifted momentum. Multiple candidates remain in single digits amid high undecided rates in recent surveys, with no candidate yet consolidating broad support ahead of the primary. Upcoming campaign events and further endorsements could still influence positioning before voting.