Background
The ranking assumption can be tested using data for the 2026 Senate elections. Consider the vote in each state for the Democratic candidate for Senate. Rank the states by the probability that the Democratic candidate wins the state. The ranking assumption says that if the Democrats win state i, they win every state ranked above state i.The ranking assumption can thus be tested by simply looking to see after the fact if the Democrats won a state ranked lower than one they lost (contrary to the ranking assumption). The following is my first ranking before the election on November 3, 2026. I have used three betting markets: Kashi, Predictit, and Polymarket.
Data collected at 10:00am on September 24, 2026
The make up of the Senate in 2022 is 53 Republicans and 47 Democrats, counting the 2 independents as Democrats. 14 states are in play according to the media, although some of these are not very close. The 14 states ranked by Kashi probabilities for the Democratic candidate are:| Probability | |||||
| state | now | Kashi | Predictit | Polymarket | |
| Georgia | D | 94 | 94 | 95 | |
| North Carolina | R | 93 | 93 | 94 | |
| Minnesotta | D | 90 | 91 | 92 | |
| New Hampshire | D | 85 | 84 | 82 | |
| Michigan | D | 74 | 70 | 74 | |
| Alaska | R | 72 | 72 | 73 | |
| Maine | R | 64 | 62 | 66 | pivot for Predictit |
| Ohio | R | 59 | 63 | 62 | pivot for Kashi and Polymarket |
| Texas | R | 57 | 60 | 59 | |
| Iowa | R | 45 | 48 | 48 | |
| Kansas | R | 31 | 37 | 33 | |
| Nebraska | R | 31 | 30 | 34 | |
| South Carolina | R | 14 | 16 | 15 | |
| Flordia | R | 11 | 14 | 13 | |
| .. | |||||
| Dem. control | R | 62 | 64 | 65 | |
The probabilities (betting odds) are quite similar across the three betting markets, and so the same story holds for each. "Dem. control" is the probability that the Democrats get at least 51 seats. For the three betting markets there is a separate contract for this. The probability that the Democrats get at least 51 seats is 62 percent for Kashi, 64 percent for Predictit, and 65 percent for Polymarket.
The ranking assumption probabilities of Dem. control are computed as follows. If the Democrats take 8 of the 14 races above, the will have 51 seats and thus control the Senate. The pivot state is Ohio for Kashi and Polymarket, with probabilities of 59 and 62 percent respectively. The pivot state for Predictit is Maine, with a probability of 62 percent. According to the ranking assumption, if the Democrats win Ohio, they will win all the states above it (or Maine for Predictit). The ranking assumption thus implies that the probability of the Democrats controlling the Senate is the probability that they win Ohio (or Maine for Predictit). The pivot probabilites of 59, 62, and 62 are close to the betting market probabilites of 62, 64, and 65. The markets are using the ranking assumption!