Welcome to “Midterm Market Monitor,” a recurring InGame feature between now and Nov. 3 in which we explore the latest and most noteworthy prediction market odds and trends related to the upcoming elections.
On America’s 250th birthday, July 4, at Kalshi, the odds suggested the Democrats taking control of both the House and Senate was not the most likely scenario. It was razor close, but “D-House, R-Senate” was trading at 39.9%, and “Democrats sweep” was 39.8%. (For what it’s worth, “Republicans sweep” was 17.3%, and the contrarian projection of “R-House, D-Senate” was a 2.1% longshot.)
But, oh, how expectations have changed. As of Tuesday morning, the Democratic sweep was trading at 61%, while Republicans holding the Senate and Democrats taking the House had dropped to 29%.
And political analysts and social media posters alike were debating what motion-in-the-ocean word best described what they’re expecting to happen in November. Are we headed for a Blue Wave? A Blue Tsunami? A Blue Hurricane? A Blue Typhoon?
Of course, 61% at Kalshi, or 66% at Polymarket as of Tuesday morning, or 62 cents at what was once the leading election prediction market available in the U.S., PredictIt, is still a far cry from 100% or 100 cents. And while some continue to claim prediction markets are some sort of powerful source of “truth,” others have observed that they mostly just echo the polls.
Collectively, though, with President Donald Trump’s approval rating hitting record lows, both the polls and prediction markets point to changing currents and a growing sense that beaches will become awash with more blue seats than red come early November.
But elections have often proven to be, ahem, unpredictable. Today’s tsunami can be tomorrow’s light trickle. With that in mind, here are several notable markets and trends this week.
Senate control
This is the body that has recently flipped in terms of the trading odds. At present, Republicans hold 53 seats in the Senate, Democrats 47. And whenever a Senate vote ends up 50-50, the vice president (presently a Republican) casts the tie-breaking vote. So Democrats needs a net gain of four seats to hold the majority in the Senate.
At Kalshi, where this market has mostly been within a couple of points in one direction or the other since March (shortly after the direct U.S. military involvement in Iran began), Democrat control crossed 60% for the first time on Tuesday:
Polymarket shows a similar pattern but an even wider gap, with Dems at 66% at press time. PredictIt sits in between the two, at 62% for the Democrats.
House control
Death, taxes, and Democrats winning the House?
The latter is actually nowhere close to a certainty. But the numbers do keep getting more and more lopsided toward the left. Heading into the midterms, the Republicans hold a narrow margin in the House of Representatives, 218-214 with two seats vacant. International Polymarket users are the most convinced that the Democrats will pick up the seats they need, climbing at press time to 93% (after the Democrats have led in the odds for the entirety of the market’s life, with the smallest lead being 57%-43% last October):
PredictIt, meanwhile, has the House going blue at 89%, with Kalshi in between the other two at 90.6%.
Race to watch: Iowa Senate
How much does polling matter? Especially in Iowa, home of the controversial 2024 poll that favored Kamala Harris over Trump and turned out to be way off base?
In the traditionally red state, where Joni Ernst is vacating her Senate seat, Republican candidate Ashley Hinson has held a lead over Democrat Josh Turek at every major prediction market all year long.
But a Marist poll released Monday night suddenly showed Turek with an 8-point lead:
Prediction market odds are tightening, but a single poll doesn’t quite have bettors convinced. Polymarket is the closest, with Hinson — a 66% favorite less than two weeks ago — up just 52%-48%. Kalshi has it 55%-45%, and it’s 57-42 at PredictIt.
This is a seat that, should it flip blue, all but guarantees Democratic control of the Senate.
Presidential election odds
Is it too early to think about 2028? Not at prediction markets!
Everyone is still something of a longshot in such a wide-open race, but Kalshi, Polymarket, and PredictIt all agree that current Vice President JD Vance is the favorite, even though, as a party, Democrats are favored over the Republicans. It’s a bit like the New York Yankees having better World Series odds than a few seemingly superior National League teams because the path to the World Series in the American League is much easier on paper.
Vance is trading at 24 cents at PredictIt and is 21% at both Kalshi and Polymarket.
The next four candidates are the same at all three sites but appear in different orders. Kalshi has Jon Ossoff at 12%, Marco Rubio at 9.7%, Alexandria Ocasio-Cortez at 9.3%, and Gavin Newsom at 7.6%. Polymarket lists them as AOC 13%, Ossoff 12%, Rubio 8%, and Newsom 7%. And PredictIt has the two Democrat frontrunners AOC and Ossoff tied at 12%, followed by Rubio at 10% and Newsom at 9%.
Wacky market of the week
This isn’t election related, but it’s politics related, and a solid sign of some of the weird stuff you can find to wager on at prediction markets. Kalshi asks:
To be clear, taking a selfie with one of his grandkids doesn’t count. The fine print says the outcome is determined by “the number of distinct days Donald Trump is photographed in a tagged editorial photo on Getty Images between Sep 21, 2026 and Sep 27, 2026.”
