The closely matched Polymarket bins around 2.65M–2.95M votes reflect trader expectations for moderate participation in Massachusetts’s safely Democratic U.S. Senate contest between incumbent Ed Markey and Republican John Deaton. A low-enthusiasm September primary, which Secretary of State William Galvin said would not lift general-election numbers, combined with typical midterm drop-off and the absence of a competitive statewide race, anchors assessments near historical baselines. Early voting from October 17–30, mail-ballot return rates, and multiple ballot questions could provide modest upward pressure, while lower turnout patterns in gateway cities and limited Democratic base mobilization remain downward risks. No late developments have yet separated the leading ranges ahead of the November 3 election.