Dan Koh's commanding 76% implied probability in the MA-06 Democratic primary stems from his dominant early positioning in the open-seat race created by Rep. Seth Moulton's Senate bid against Ed Markey. As a former Biden White House deputy and Marty Walsh aide, Koh has secured high-profile endorsements from Pete Buttigieg, Kamala Harris, and IBEW Local 2222, while raising over $200,000 in January alone—outpacing rivals' combined totals—and becoming the first candidate to qualify for the September 1 ballot by gathering more than 2,000 signatures in late March. In this crowded field of nine Democrats, including state Rep. Tram Nguyen and self-funded fintech executive John Beccia, Koh's fundraising edge and establishment support reflect trader consensus on his frontrunner status, though additional qualifiers and forums could shift dynamics.