The closely matched probabilities between the 4M-4.25M and 4.25M-4.5M brackets reflect uncertainty over midterm turnout in a safe Democratic seat following Dick Durbin’s retirement. Democratic primary participation rose sharply to roughly 1.15-1.28 million votes, a notable increase from 2022 levels amid a contested nomination won by Juliana Stratton, while Republican primary engagement declined. This enthusiasm gap, combined with Illinois’s established early voting period beginning September 24 and no-excuse mail options, supports expectations near historical midterm averages around 45 percent of eligible voters. A non-competitive general election between Stratton and Republican Don Tracy limits additional mobilization, though registration trends, suburban turnout patterns, and any late national developments could still shift final totals within the narrow leading ranges.