Trader consensus heavily favors Dan Koh at 76.5% implied probability to win the open Massachusetts 6th Congressional District Democratic primary on September 1, driven by his dominant early fundraising—over $2 million raised in his launch quarter—and status as the first candidate to qualify for the ballot last week with signatures from all 39 district cities and towns. Incumbent Seth Moulton vacated the seat for a U.S. Senate primary challenge against Ed Markey, creating a crowded field of nine Democrats including state Rep. Tram Nguyen and veterinarian Mariah Lancaster, who trail at 5.3% and 9.9% amid limited polling. Recent local endorsements, like Swampscott Select Board Vice Chair Doug Thompson's backing, bolster Koh's grassroots momentum in this competitive North Shore race, though upcoming forums and whip counts could shift dynamics.