US Politics Odds: Democrats odds-on for House and Senate control in historic midterm market shift

Spokesperson for William Hill, Lee Phelps, said: “The Democrats are now as close to nailed on as we have ever had them in the House market. Their 1/16 price is the shortest we have seen at this stage of a midterm election cycle, and with 86% of all bets backing them, punters are in no doubt about where control of the House is heading.

“The writing has been on the wall for Republicans for some time. When we opened the House market in May 2025, Democrats were already a historically short 1/9, and the price has continued to collapse as the election has moved closer.

“The Senate move has been just as remarkable. Democrats opened at 5/2, equating to a 28% chance of winning the chamber, but have been cut into 4/9, giving them an implied probability of around 69%.

“What makes that particularly interesting is that just 32% of Senate bets have backed the Democrats. We took a number of bets on Republicans at odds-on prices between 1/3 and 8/13, so plenty of customers may now be sitting on positions that looked very strong at the time but are being caught out by the market’s dramatic reversal.”

The wider prediction-market picture also indicates significant momentum towards Democratic control. Current exchange markets put Democrats at roughly 91% to 93% to win the House and about 63% to take the Senate, with a Democratic sweep of both chambers the most likely overall outcome.

All 435 House seats and 35 Senate seats are due to be contested on 3 November. Democrats need a net gain of three House seats and four Senate seats to control the respective chambers.

William Hill Midterms Balance of Power Odds:

Democrats House & Senate – 2/5

Democrats House & Republican senate – 7/4

Republican House & Senate – 9/1

Republican House & Democrat Senate – 66/1

Bet on William Hill US midterm markets

*Odds subject to change – prices correct at time of writing.