Dan Koh leads trader consensus in the Massachusetts 6th Congressional District Democratic primary due to his dominant fundraising edge—nearly $3.5 million raised—and early endorsements from local officials and unions, positioning him ahead of a crowded field for the open seat vacated by Rep. Seth Moulton’s Senate bid. State Rep. Tram Nguyen trails as the main challenger, drawing support in some internal polls amid roughly 46 percent undecided voters, while John Beccia and others register lower shares. Recent campaign polls underscore the fragmented contest ahead of the September 1 primary, with Koh’s resource advantage shaping expectations for consolidation of support among Democratic primary voters.