The competitive open-seat Michigan Senate contest between Democrat Abdul El-Sayed and Republican Mike Rogers, rated a toss-up in recent polling averages, anchors trader expectations for turnout in the low-to-mid 4 million range. Midterm participation has historically fallen well below the 5.7 million ballots cast in the 2024 presidential election, yet elevated Democratic primary engagement exceeding 1.5 million votes in August signals sustained interest that could limit the typical drop-off. Both campaigns face pressure to mobilize irregular and low-propensity voters amid economic and foreign policy concerns, while a clean voter file supports steady registration levels. These crosscurrents keep probabilities clustered between the 4.4 million and 5 million bins, with separation likely hinging on late-cycle enthusiasm gaps or get-out-the-vote intensity through November.