Trading across the 2026 midterm prediction markets is concentrated on a relatively small group of races, with Senate contests accounting for much of the recent activity.
But the markets attracting the most trading are not necessarily the most competitive. Some heavily traded races have a clear favourite, while others are priced much closer to 50-50.
This analysis looks at which 2026 midterm prediction markets are attracting the most recent activity, comparing the busiest Senate and governor markets and exploring why trading volume is concentrated in certain races.
The markets are ranked by trading volume over the latest seven-day period, rather than their total lifetime amount, to show where trading is currently concentrated.
For the latest prices and trading activity across individual Senate and governor races, visit iPredicta's US midterms prediction markets page.
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Most actively traded 2026 midterm prediction markets
Seven of the 10 highest-volume markets in the snapshot below are Senate contests. Three governor races appear, with California the highest placed of them.
| Race | Market | Seven-day trading volume |
|---|---|---|
| Maine | Senate | $565,664 |
| Alaska | Senate | $428,777 |
| California | Governor | $296,014 |
| Michigan | Senate | $249,663 |
| Iowa | Senate | $215,928 |
| Texas | Governor | $184,956 |
| Kansas | Senate | $184,286 |
| Texas | Senate | $175,612 |
| Ohio | Senate | $142,772 |
| Florida | Governor | $137,578 |
Seven-day trading volume for the seven days to 28 September 2026, as published on the iPredicta US Midterms prediction markets page. The figures are Polymarket's own seven-day volume, summed across the matching markets for each state. Volumes can change quickly as trading continues.
These figures cover Polymarket only. Kalshi does not publish a comparable seven-day volume figure that we can read, so the ranking below describes where Polymarket's trading is concentrated rather than the market as a whole. A race that is quiet on Polymarket may be busier elsewhere, and this table cannot tell you so.
What is driving trading activity in the 2026 Senate markets?
Senate contests dominate the most actively traded 2026 midterm prediction markets, and the concentration is more telling than the individual rankings. A relatively small group of Senate races accounts for a large share of recent trading activity, rather than volume being spread evenly across the 2026 Senate map. The order within that group changes from week to week, which is itself a reason to read the table as a snapshot rather than a standing.
It is hard to pinpoint a single characteristic shared by all of these markets, but several have features that make them particularly significant or uncertain.
Ohio is a special election to complete Vice President JD Vance's former Senate term. Reuters reported figures from the advertising tracker AdImpact showing that around $298 million had been spent on advertising in the race by mid-September, more than any other Senate race this cycle. The contest between Republican Jon Husted and Democrat Sherrod Brown has remained closely contested in recent polling, and the combination of a highly competitive race, substantial campaign spending and a seat that could be important to control of the Senate has made Ohio one of the most closely watched contests.
Texas offers a different reason for sustained interest. Democrats have not won a Senate election in the state since 1988, but the 2026 contest has developed into a much more competitive race than that history might suggest. Democrat James Talarico has led Ken Paxton in a number of recent polls, with the margins generally remaining narrow. The result is a race where the current polling picture differs significantly from Texas's recent electoral history, giving traders a very different set of expectations to assess.
Iowa is an open-seat contest following Joni Ernst's retirement. Alaska and Maine both use ranked-choice voting for their federal elections, and Alaska's general election follows a top-four primary. Those mechanics give traders a different set of factors to assess from the more conventional two-candidate Senate contests elsewhere on the map, although a voting system does not by itself explain why a market is busy in any particular week.
The wider Senate picture is another factor. The outcome of individual races can affect the number of possible paths to control of the chamber, so a market does not necessarily need to be close to 50-50 to attract heavy trading. A race can still be heavily traded if its result could materially affect the overall Senate balance.
For a closer look at the 2026 Senate prediction markets, including the latest prices across the major contests, see our dedicated analysis.
Which governor markets are attracting the most trading?
Three governor markets appear among the 10 highest-volume 2026 midterm markets: California, Florida and Texas.
California stands out, recording $296,014 in trading over the latest seven-day period, the highest of the three. Yet the market is not particularly close: Democrat Xavier Becerra leads it by a wide margin.
The volume in California is interesting because it reflects the evolution of the market rather than uncertainty over the current favourite. The race began with a large field of candidates competing in California's top-two primary, before Becerra and Republican Steve Hilton emerged as the two candidates advancing to November's elections. The substantial trading activity therefore spans a market that has changed considerably as the field has narrowed and expectations have become more concentrated.
Florida and Texas show a similar pattern on a smaller scale, with Republicans Byron Donalds and Greg Abbott leading markets that have still attracted six-figure seven-day volumes despite having a clear favourite.
That contrasts with races where the leading candidates are priced much closer to 50-50. The governor markets therefore show that trading volume can be driven by more than uncertainty over who will win. The size of the market, changes in the candidate field and the amount of activity around a race can all contribute to trading, even when one candidate has established a substantial lead.
Why does prediction market trading volume matter?
Trading volume provides another way to understand prediction markets beyond the headline probability. While the price shows how a market currently assesses an outcome, volume indicates where participants are actively trading and which races are attracting the most attention.
The distinction between recent and lifetime volume is particularly important. A market can have accumulated substantial trading over several months without currently attracting much activity, while a lower-volume market may be seeing a sharp increase in interest as the election approaches. Looking at seven-day volume therefore provides a snapshot of where trading activity is concentrated now, rather than simply which markets have been around the longest.
The difference can be seen in the governor markets. California recorded the highest seven-day trading volume of the three at $296,014, but that represented only around 0.7% of its lifetime trading activity. Florida, by comparison, had a smaller seven-day volume of $137,578, but around 61% of its lifetime trading had taken place during the latest week. This shows why recent volume can tell a different story from the lifetime total.
Volume can also provide useful context when comparing markets. A substantial change in the price of a heavily traded market may reflect a broader shift in expectations, while movements in a lightly traded market may provide less evidence of a wider trading consensus. For a deep dive on this, check out our What Are Prediction Markets? guide.
For the 2026 midterms, trading volume is a useful companion to prediction-market prices. It helps identify where market attention is concentrated and, when tracked over time, whether that attention is increasing or fading.
What are the most active 2026 midterm prediction markets telling us?
The most actively traded 2026 midterm markets are concentrated in a relatively small number of Senate and governor races, but the reasons for that activity vary.
Some markets are attracting volume because they are closely priced, while others have generated sustained interest despite a clear favourite. California's governor market is one of the clearest examples: Becerra leads it comfortably, yet it recorded $296,014 in trading over the past seven days.
The data also shows why recent trading volume can add useful context to prediction-market prices. Looking at the latest seven-day activity highlights where traders are currently concentrating their attention, while comparing that activity with market prices helps distinguish between closely contested races and high-profile markets that are attracting volume for other reasons.
It is also worth treating the order itself with some caution. Seven-day volume can move sharply from week to week, and a market near the top of this table may not be near the top of the next one. The concentration is the durable observation; the ranking is a snapshot.
As the election approaches, changes in both trading volume and market prices could provide useful signals about where prediction-market activity is increasing or fading.
For the latest prices across individual governor races, control of Congress and other 2026 election markets, visit iPredicta's US Midterms prediction markets page.
