Traders in the prediction markets are betting that the Democrats have their best opportunity to take over the Senate since April. On Kalshi, speculators now put the party’s chances at 55%, which comes close to the level reached in mid-April. Polymarket shows an even higher expectation for the Democrats, giving them a 59% chance to seize control.
Republicans are holding onto their upper-chamber advantage for now, even as the fight for the U.S. Senate stays close. They are defending majorities in both the House of Representatives and Senate this November, though the Senate race has long been seen as harder ground for Democrats to conquer. Republicans currently control 22 of the 35 Senate seats on the ballot this year, a position strengthened by two special elections in Ohio and Florida. To wrest control, Democrats would need to turn several seats in states where President Donald Trump ran ahead by 10% or more in 2024, including Alaska, Texas and Ohio.
The Odds Have Improved
On prediction markets, the chances of the Democrats taking control of the Senate have grown much stronger since 2026. Before the war with Iran broke out on Feb. 28, Republicans held roughly 60% odds of keeping the Senate across both Kalshi and Polymarket. Those odds fell as fuel costs rose and pushed down President Trump’s approval numbers.
In April, the odds that Democrats would win the Senate exceeded Republican odds of holding onto control, but the GOP’s prospects rebounded in May and carried on recovering through the summer as the United States and Iran pulled back from their war, which helped ease pressure on gas prices. The recovery held through the spring and early summer months, with both sides stepping back from direct conflict and prices stabilizing.
The Recent Polls Favor Democrats
A number of recent polls now suggest Democrats sit in a favorable position as November approaches. Released Wednesday, a New York Times/Siena University survey found likely voters nationwide favoring Democratic candidates over Republicans in their congressional districts by roughly 9 percentage points.
The poll data comes alongside a broader shift in the political environment. Gasoline is above $4 a gallon nationally, diesel prices are at an all-time high, and U.S. oil prices are now above $100 per barrel. Those numbers matter for the Senate fight because they shape voter sentiment, and traders now think gas prices will hit new highs this year.
What Trump’s Approval Rating Tells Us
Throughout the year, Trump’s approval rating has shaped the Senate odds. Rising fuel costs in February drove approval ratings down, and that dip showed up in the prediction markets. As prices climbed, the likelihood of a Republican Senate holding declined. Once the U.S. and Iran de-escalated the war, approval ratings recovered, and GOP odds bounced back.
Now the cycle is reversing again. U.S. oil prices are above $100 per barrel, gasoline is above $4 a gallon nationally, and diesel prices are at an all-time high. Prediction market traders now think gas prices will hit new highs this year. That shift is already visible in the odds: Democrats have a 55% chance on Kalshi and a 59% chance on Polymarket.
The Seats Up For Grabs
This year, Republicans hold 22 of the 35 Senate seats on the ballot. Democrats would need to capture several seats in states where Trump won by 10% or more in 2024, including Alaska, Texas and Ohio, to seize majority control.
A route is available, even if it demands Democrats run in areas where the party has traditionally lagged behind.
The Iran War And Its Aftermath
On Feb. 28, the Iran war broke out, and its effects were felt almost immediately in the Senate race. Prior to the fighting, Republicans sat at roughly 60% chances of keeping control of the Senate across both Kalshi and Polymarket. The conflict pushed gasoline costs upward, which then pulled down Trump’s approval numbers.
Approval ratings and GOP odds both recovered as a result of the U.S. and Iran stepping back from the conflict, an event that occurred in May and continued through the summer.
The Prediction Market View
Kalshi gives Democrats a 55% chance and Polymarket puts them at a 59%, and both readings reflect what traders think will happen rather than actual predictions. Those numbers shift with news, prices and polling. Right now, it is the highest Democrats have reached since mid-April.
Since February, the markets have changed their position. Prior to the war with Iran, Republicans had roughly 60% chances of keeping control of the Senate. Today, Democrats lead on both sides of the political equation.
Key Facts Box
- Democrats: 55% chance to win the Senate on Kalshi
- Democrats: 59% chance to win the Senate on Polymarket
- Republicans: 60% odds to hold the Senate before the Iran war began on Feb. 28
- Republicans control 22 of 35 Senate seats up for election this year
- U.S. oil prices above $100 per barrel
- Gasoline above $4 a gallon nationally
- Diesel prices at an all-time high
- New York Times/Siena University poll: Democrats +9 percentage points over Republicans
The battle for the Senate continues. However, the betting markets are signaling something clear: Democrats now sit at their most advantageous position there since April, with the odds having shifted in their favor. The next few weeks will determine if the surveys stand firm, the wagers increase still, and the upper chamber changes hands.
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