The 2022 U.S. Senate Elections will be held in one week on Tuesday, November 8, 2022. Below we’re comparing probabilities from forecast models, prediction markets, and bookmakers for the Republican candidate in the 35 Senate races on the ballot. The table contains the win probabilities from:
- Two election forecasts (FiveThirtyEight & Decision Desk HQ)
- Five betting platforms (William Hill, Coral, Betfred, Smarkets, & SBK)
- Three prediction markets (PredictIt, Polymarket, & Insight Prediction)
- One forecasting platform (Metaculus)
Please note that because prediction markets and bookmakers have fees built into their prices and odds (the “vig” or bookmaker’s margin), their implied probabilities total over 1.0 and both Republicans and Democrats can have implied probabilities above 0.5 in the same race.
| state | 538 | DDHQ | William Hill | Coral | Betfred | SBK | Smarkets | PredictIt | Insight | Polymarket | Metaculus |
| Alabama | 1.00 | 1.00 | 1.00 | ||||||||
| Alaska | 1.00 | 1.00 | 0.99 | 1.00 | 0.98 | 0.98 | 0.98 | ||||
| Arizona | 0.31 | 0.30 | 0.52 | 0.52 | 0.50 | 0.52 | 0.52 | 0.49 | 0.48 | 0.42 | 0.35 |
| Arkansas | 1.00 | 1.00 | 1.00 | ||||||||
| California | 0.00 | 0.00 | |||||||||
| Colorado | 0.09 | 0.11 | 0.20 | 0.15 | 0.14 | 0.13 | 0.14 | 0.12 | 0.14 | ||
| Connecticut | 0.01 | 0.01 | 0.03 | ||||||||
| Florida | 0.93 | 0.91 | 0.95 | 0.94 | 0.95 | 0.96 | 0.96 | 0.94 | 0.96 | ||
| Georgia | 0.53 | 0.48 | 0.56 | 0.60 | 0.60 | 0.59 | 0.60 | 0.58 | 0.60 | 0.53 | 0.42 |
| Hawaii | 0.00 | 0.00 | |||||||||
| Idaho | 1.00 | 1.00 | |||||||||
| Illinois | 0.01 | 0.02 | 0.05 | ||||||||
| Indiana | 0.97 | 0.99 | |||||||||
| Iowa | 0.95 | 0.99 | 0.97 | 0.96 | 0.96 | 0.96 | 0.96 | ||||
| Kansas | 0.99 | 1.00 | |||||||||
| Kentucky | 1.00 | 1.00 | |||||||||
| Louisiana | 0.99 | 1.00 | |||||||||
| Maryland | 0.00 | 0.00 | |||||||||
| Missouri | 0.99 | 0.97 | 0.99 | 0.97 | 0.98 | 0.97 | 0.98 | ||||
| Nevada | 0.53 | 0.50 | 0.65 | 0.75 | 0.71 | 0.68 | 0.69 | 0.68 | 0.59 | 0.60 | 0.55 |
| New Hampshire | 0.24 | 0.29 | 0.27 | 0.31 | 0.27 | 0.29 | 0.31 | 0.28 | 0.32 | 0.24 | |
| New York | 0.01 | 0.00 | |||||||||
| North Carolina | 0.78 | 0.71 | 0.89 | 0.89 | 0.89 | 0.90 | 0.90 | 0.90 | 0.71 | 0.87 | |
| North Dakota | 1.00 | 1.00 | |||||||||
| Ohio | 0.78 | 0.76 | 0.83 | 0.88 | 0.91 | 0.88 | 0.88 | 0.86 | 0.81 | 0.83 | 0.75 |
| Oklahoma | 1.00 | 1.00 | |||||||||
| Oklahoma (Special) | 1.00 | 1.00 | |||||||||
| Oregon | 0.01 | 0.02 | 0.06 | ||||||||
| Pennsylvania | 0.41 | 0.56 | 0.64 | 0.64 | 0.65 | 0.65 | 0.67 | 0.64 | 0.60 | 0.56 | 0.42 |
| South Carolina | 1.00 | 1.00 | |||||||||
| South Dakota | 1.00 | 1.00 | |||||||||
| Utah | 0.95 | 1.00 | 0.90 | 0.87 | |||||||
| Vermont | 0.00 | 0.00 | 0.06 | 0.02 | |||||||
| Washington | 0.08 | 0.08 | 0.17 | 0.18 | 0.19 | 0.18 | 0.14 | ||||
| Wisconsin | 0.77 | 0.92 | 0.89 | 0.89 | 0.88 | 0.89 | 0.88 | 0.88 | 0.64 | 0.83 | 0.66 |
The probabilities are all generally close together. The only races where the platforms disagree about whether the Republican Senate candidate should or should not be above 0.50 are four swing states: Arizona, Georgia, Pennsylvania, and Nevada. (While DDHQ’s Nevada GOP win probability rounds up to 0.50, it is listed at 0.498677417114376.)
There are only four senate races where the difference between the minimum and maximum probabilities of the GOP winning are greater than 0.20:
- Arizona: 0.21-0.22 gap between the election models (FiveThirtyEight & DDHQ) and several bookmakers (William Hill, Coral, SBK, Smarkets) confident in the GOP’s chances.
- Nevada: 0.25 gap between DDHQ (0.50) and Coral (0.75).
- Pennsylvania: 0.23-0.26 gap between FiveThirtyEight and all five bookmakers and PredictIt.
- Wisconsin: 0.26 gap between DDHQ and Insight Prediction. This was relatively unique in the DDHQ was the most confident in the Republican’s chances, while a prediction market was the least.
Out of all 11 platforms, FiveThirtyEight has the lowest probability for Republicans in 24 out of 35 senate races.
Below is some background on the data sources used:
FiveThirtyEight
Nate Silver’s election forecasts are the most well-known, if not the most influential, in American politics. The probabilities used are the latest available from the 2022 Senate state topline output for the “Deluxe” model and rounded to the nearest hundredth. States with multiple Republican candidates in the general election – Alaska with Ranked Choice Voting and Louisiana with its “jungle primary” – include the aggregate of the probabilities for all Republican candidates.
Decision Desk HQ
Decision Desk HQ is a provider of election returns and data. They were the first to call the US Presidential election for Trump in 2016 and Biden in 2020. Probabilities come from their 2022 Senate model and are rounded to the nearest hundredth.
Smarkets & SBK
Smarkets is a British online betting exchange that allows peer-to-peer wagers on sports and politics. SBK is a British sport betting app created by Smarkets that draws on Smarkets’ exchange for pricing, and both share the same political betting guru, Matthew Shaddick. Odds from both were retrieved from oddschecker.com, converted into implied probabilities, and rounded to the nearest hundredth.
William Hill, Coral, & Betfred
William Hill, Coral, and Betfred are three established British bookmakers. Political gambling is legal in England (unlike the United States) and the British love betting on American politics. Odds from all three were taken from oddschecker.com and converted into implied probabilities.
PredictIt
PredictIt is a political prediction market run by the Victoria University of Wellington, New Zealand, and Aristotle International of Washington, DC. PredictIt traders can buy “Yes” and “No” shares on whether each party (typically “Democratic” and “Republican”) will win the U.S. Senate election in a particular state. A correct prediction receives $1/share, and a wrong prediction receives $0/share. The individual share prices can indicate what traders believe is the probability of the respective party winning the election. Because each contract has multiple share prices, the following formula was used to find an estimated price for one individual contract:
(bestBuyYesCost + (1-bestBuyNoCost) + BestSellYesCost + (1- BestSellNoCost)) / 4
Polymarket
Polymarket is a decentralized prediction market built on the Polygon blockchain. Traders buy and sell using a stablecoin pinned to the U.S. dollar. Polymarket was forced to shutter its U.S. operations in January 2022, but trading is open to persons outside the United States. Prices were taken from Polymarket Whales.
Insight Prediction
Insight Prediction is the new prediction market on the block. Founded by Douglas Campbell, an economics Ph.D. looking to build a prediction market with more interesting markets than PredictIt (“Will Russia Take Bakhmut by November 25th?”) and more liquidity than Polymarket. US persons are currently excluded from trading on Insight Prediction. Prices used are the “latest yes price” for Republican contracts and were rounded to the nearest hundredth (Insight prices go to the thousandth place).
Metaculus
Metaculus is a forecasting platform that aggregates predictions by encouraging users to compete in predicting probabilities on certain questions of “global importance.” No money is charged or exchanged, although certain contests have cash prizes. Participation is generally low, with 179 total forecasters predicting the Pennsylvania Senate election probabilities. Probabilities used are the median unweighted community prediction for each market.
As always, there are a few caveats:
The table above is for informational purposes only. Please note again that the numbers used are rounded to the nearest hundredth place, so some differences in predictions may not be distinguishable here. Additionally, some of the data is taken from third-party sites. If you would like to do further research, please go to each platform directly. And lastly, these probabilities are for Republican candidates only. Two candidates can have an implied probability above 0.50 because bookmakers and some prediction markets have fees built into their odds or prices.