Forecaster Who Called Trump's 2024 Win Now Gives Democrats a 78% Shot at the Senate

Thomas Miller, a Northwestern University data scientist and professor who correctly forecast Trump's 2024 win and the 2021 Georgia runoffs, now gives Democrats a 78% chance of winning control of the Senate in next month's midterms, up from 71.5% on October 14. Republicans' odds of holding the majority have fallen from 36% in mid September to about 22.5% by late October, according to his latest forecast, which he began publishing October 22 after refining the underlying methodology since mid September.

Miller builds his forecasts from betting market data on Kalshi and Polymarket, the two highest volume prediction markets, adjusting the prices statistically and running a time series analysis meant to capture 80% to 90% of what is driving shifts in the odds. His model currently has Democrats leading in 18 of the 35 Senate races on the ballot this year to Republicans' 17, a split that would flip the chamber from its current 53 to 47 Republican majority to a 52 to 48 Democratic one.

Democrats are favored in North Carolina, Ohio, Texas, Alaska, and Maine, while holding comfortable leads in Michigan, at 68.6%, and Georgia, at 94.9%. By comparison, Kalshi's own betting markets currently put Democrats' odds of winning the Senate at 63%, well below Miller's 78% estimate.

Miller has attributed much of the recent movement to races shifting together based on the president's day to day actions rather than moving independently on local dynamics, suggesting what he calls a Trump effect may be working against Republicans more broadly. He has cautioned that the odds remain extremely volatile and could shift substantially before Election Day.