Michigan Senate winner? — In 2026

The Michigan Senate market on Polymarket and Kalshi asks who will win the open 2026 U.S. Senate seat being vacated by Democrat Gary Peters. On Polymarket, the Democratic nominee is priced at 73.5% with the Republican at 27.5%, while Kalshi has the Democratic party at 70.0% and the Republican party at 31.0%. The cross-platform spread is modest — roughly 3.5 points on the Democratic side and 3.5 points on the Republican side — with Polymarket slightly more bullish on Democrats. The Democratic side is the clear favourite, consistent with the state's recent partisan history: Republicans have not won a Michigan U.S. Senate race since 1994 and have not won this seat since 1972, and have not won a non-presidential statewide race in Michigan since 2014. Still, as one of only two seats up held by a Democrat in a state that voted for Trump in 2024, Michigan is considered a key Senate battleground in 2026, which explains why the Republican tail is priced meaningfully above zero. The August 4 primary is looming: Congressman Mike Rogers is the decisive favorite to win the Republican nomination, two years after he narrowly lost the 2024 Senate race to Elissa Slotkin, while the Democratic primary features a contested battle between Mallory McMorrow, Abdul El-Sayed, and Haley Stevens. General-election polling remains tight — the Pollsmax average sits at 44.3% D / 43.9% R, a Democratic margin of just 0.4 points — a contrast with the roughly 70–73% party-win odds that reflects markets weighting Michigan's structural Democratic lean over current head-to-head numbers. Overall, the two venues agree directionally, with only minor pricing daylight between them.