The closely matched Polymarket bins for Massachusetts Senate turnout reflect uncertainty in a low-competition general election where Democratic incumbent Ed Markey holds a wide lead over Republican John Deaton in recent polling. A lopsided Democratic primary featuring Markey and Seth Moulton has produced limited enthusiasm, with Secretary of State William Galvin noting it will not drive unusually high participation. Factors such as early voting volumes, mail ballot return rates, and typical midterm drop-off in a safely Democratic state continue to shape trader assessments, with no major late developments yet separating the leading ranges around 2.65M–2.95M votes. Historical midterm totals near 2.5 million provide a baseline, while expanded early and mail options from the 2022 cycle could modestly lift participation depending on registration trends and mobilization in urban areas.