One of the most discussed talking points in the run-up to the 2026 Midterm elections is the value of prediction market election odds. With quantitative models out there and straight polling averages, the debate about whether prediction markets tell us anything rages every so often. But American polling isn't that accurate, and unlike in other countries, it can’t be taken to the bank the same way; and if quantitative models use potentially bad polling, how reliable can they be?
Where the 2026 midterm odds stand today
It’s worth starting with what basically everyone agrees on. Democrats are overwhelming favorites to win the House, regardless of the source. Prediction markets have that chance at around 10%, which is where the models broadly are. Generic Ballot polling says Democrats are winning by ~9% per Nate Silver’s average, which would mean even a clear and sizeable polling miss would still see a Democratic House.
Everyone broadly agrees that the Democrats are Senate favorites too, but much more narrowly. Prediction markets have that at 62%, which isn’t far from quant models putting Democrats in the 55%-65% range. But it gets wonky at the individual race level.
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Why markets and polls are diverging in key Senate races
Iowa’s hotly contested Senate seat is the best example. Democrat Josh Turek leads Silver by 2.1% in Silver’s polling average and is up 8% in the highest-quality poll of the race so far, from Marist. Kalshi’s Iowa Senate odds put his chance of winning at 41%. No scandal or black swan event has happened since the polls were taken; the market just doesn’t buy the polls.
And the crazy thing is, that’s not a stupid price.
Ann Selzer, the Queen of Iowa polling, had Kamala Harris winning Iowa in 2024, before she lost the state by 13%. Most polling, though not Selzer's, had the state as a toss-up in 2020, before Trump won comfortably. Should someone really believe in Iowa’s polling? It’s certainly debatable!
Another example is South Carolina, where Darline Graham, sister of former Senator Lindsay, is facing a challenge. Two polls from Republican aligned pollsters - Trafalgar and Insider Advantage - are showing the race within 2%, the kinds of results that would normally cause some excitement. And yet, the market’s basically unchanged at 87% for Graham to win a full term.
The problem all comes back to the last time these Senate seats were up, six years ago.
The lasting impact of recent election polling misses
Nobody trusts the polls because they were absolutely terrible the last time these Senators were up for re-election. Joe Biden was in a toss-up position in Texas, Susan Collins hadn’t led a poll all cycle in Maine, and Democratic Senate candidates were there or thereabouts in the lead in polls of Montana, Kansas, South Carolina, Alaska, and Texas, before failing to come within 8% of winning any of them.
In Iowa, Democrats lost by 6% in a state they led most of the polls that year, while Cal Cunningham lost because of a sex scandal in North Carolina. What was supposed to be a simple Senate flip given the polling came down to a double-barrel Senate runoff in Georgia that narrowly delivered a 50/50 Senate.
The divergences between the polls and the markets all come back to one number you see constantly if you are on elections-oriented social media or anywhere discussing this year's probable outcomes. It’s 413 - the number of Electoral College votes Joe Biden was projected to get by some in 2020. He would get 306, losing six states compared to the maximalist projections. Of those six, three of them - Texas, Ohio, and Iowa - are core swing states this year in the battle for Senate control.
Is any of that 2020 context relevant to whether the polls are right or wrong this year? No, or at least it shouldn’t be. 2020 was a wildly anomalous year because of COVID and the issues it created worldwide, and polls were better in 2024 (though not perfect). Polls in the 2022 midterms were broadly good, and where they were biased, it was against Democrats in swing states. But the 2020 context is wildly important in understanding why the markets are doing what they’re doing.
The market plainly doesn’t believe the polling.
Identifying value and potential betting opportunities
If the polls right now reflect what happens on election night, then Democrats will have been undervalued. That statement is wrong in two ways: the polls are right as a snapshot of this moment in time, but events change, and Republicans recover, or they’re just wrong again. But if they reflect what will happen in November, then multiple Democratic candidates in the 40-65% odds range will end up winning their seats.
If they’re reflective of reality, we’ll look at Sherrod Brown in Ohio only being 62% odds to win despite leading by 5% in the polls as a laughable underprice, and seats like Nebraska and South Carolina and Kansas, where Democrats are in rough tossups but priced as big underdogs, will be the stories of election night. But that doesn’t mean the markets are wrong.
Polls change outcomes as much as they reflect reality. The run of bad polls for Republicans in what should be safe seats likely means the GOP will play defense there - spending a bit of cash, sending Trump or Vance to rallies, and generally focusing some resources there. So even if the “true” price of Democrats winning South Carolina if the election were held today is, say, 40%, it’s highly likely that Republicans would still win it easily by November 3rd. And that’s the true value of prediction markets - not reflecting where things are now, but where they’ll end up.
And in a world where the mantra of Trust The Polls doesn’t have a great track record, it’s compelling to see 2026 midterm odds through another lens.
