The 2026 IL-12 election produced a Republican margin of roughly 39 points, with incumbent Mike Bost at 69.5% and Democrat Julie Fortier at 30.5%, landing squarely in the 35-40% band that traders priced at 74%. The district’s consistent Republican lean, shown in prior cycles with margins above 40 points and 2024 presidential results around R+43, anchored expectations. Forecasters rated the seat Solid or Safe Republican well before Election Day, reflecting Bost’s fundraising edge of over $1.6 million versus Fortier’s $162,000 and the absence of competitive polling shifts. With results certified shortly after November 3 and no late-breaking developments altering the baseline, the market’s heavy weighting on the 35-40% outcome mirrors the predictable scale of Republican performance in this southern Illinois district.