Former President Joe Biden’s May 4 endorsement of Dan Koh, along with support from Kamala Harris and End Citizens United, has consolidated Democratic donor and activist backing behind the former White House aide in the September 1 primary for Massachusetts’ 6th Congressional District. Koh’s early ballot qualification, leading fundraising totals, and endorsements from local officials have further distended his advantage over a fragmented field that includes Kevin Larivee, Rachel Creemers, and Tram Nguyen. Traders reflect this positioning through elevated odds for Koh, consistent with historical patterns in open-seat Democratic primaries where early institutional support narrows the contest quickly. The September primary date leaves room for late developments, though no major shifts have emerged in the past week.