Dan Koh leads the MA-6 Democratic primary field with a substantial polling advantage and the largest campaign war chest, holding roughly $3.6 million in cash on hand. Recent internal surveys conducted in late July and early August 2026 showed him at 34 percent support, nearly double his nearest rivals, after earlier spring polls reflected a more fragmented race with high undecided shares. Key factors include Biden’s endorsement, heavy television advertising, and broad donor support from outside the district. Tram Nguyen remains the clearest alternative, drawing on local organizing and prior polling strength, while the remaining candidates trail with minimal reported momentum or resources. The September 1 primary timing concentrates attention on late-cycle shifts in voter preference and turnout.