Ohio Senate (special)

Both models take the same public polling and the same seat map, and each one's control number sits inside the range its own seat probabilities imply. So the gap is not about how seats combine; it is the sum of seat-level differences. Kansas is widest: FiftyPlusOne's number fell from 51.2% to 48.7% in its October 26 reading, against DDHQ's 23% and Kalshi's 39.5%, both unchanged since October 24. Against the five-aggregator poll average of Hamilton +0.8, FiftyPlusOne takes 1.0 point off his lead, Kalshi 2.5 and DDHQ 5.6. In Ohio the poll average is Brown +3.8; DDHQ's model takes 3.6 points off his lead, FiftyPlusOne, down from 64.5% to 62.7%, takes off 1.7, and Kalshi, unchanged at 67.5%, takes off 0.9. In Maine, where the poll average is Jackson +2.0, DDHQ takes 1.5 points off his lead and FiftyPlusOne adds 1.2; Kalshi fell from 60.5% to 59.5% and takes 0.4 off. Expected Democratic seats are 50.5 for DDHQ and 51.5 for FiftyPlusOne, either side of the majority line. Kalshi (63.5%, up 1 point since October 25) and Polymarket (64.5%, down 2) are still between the two models. FiftyPlusOne's control number fell from 73.5% to 72.4% in the same reading, which narrowed the spread from 19.5 points to 18.4.

• Maine is where structure and polling point opposite ways: incumbents in Collins's position have lost 8 of 9 midterm races since 2006, but her 2020 result beat the final polling average by 12 points.
• Ohio and Kansas turn on how far to mark down a Democratic poll lead in a state Trump carried. The record runs from 2 to 3 points in the contested midterm races of 2018 and 2022 to 5.3 across all Republican-state midterm races since 2014. Brown adds a wrinkle: in 2024 he ran 7.6 points ahead of the top of the ticket and still lost by 3.6.
• Timing: DDHQ's reading is dated October 2. Its page showed no newer one when read on October 3 and 4, and the daily reader has recorded no newer reading on any day from October 5 to 26, so a newer DDHQ number, if one exists, is not on the board. FiftyPlusOne's is dated October 26. Every poll published in between, including New York Times/Siena surveys of Alaska and Ohio fielded through October 1 and YouGov's Kansas survey fielded through October 4, may be in one and not the other.
• A third model sits with FiftyPlusOne. Silver Bulletin's Deluxe forecast, read once on October 4 from its subscriber page and not a board source, has control at 72.8% and publishes projected margins, so its markdown can be read directly: it adds 0.8 points to its own poll average in Maine and takes 2.1 off in Kansas and 0.4 off in Ohio, nearer FiftyPlusOne's inferred markdowns than DDHQ's in all three. Its Classic version, without expert ratings, has control at 70.0% and differs by 0.2 to 0.7 points in those seats, so expert ratings, which FiftyPlusOne also uses, are worth 2.8 points of control inside Silver Bulletin's model, against a gap of 18. Agreement between two models identifies DDHQ as the one that differs and leaves open which is closer to the result.

Every source reads the same polls. Turning each probability back into a margin shows what it does to them. The market takes 2.5 points off the Democrat in South Carolina and Kansas, 1.3 in Iowa and 0.9 in Ohio, adds 0.1 in Texas, and adds 1.7 to Peltola's lead in Alaska, where its price is 74.5% against a poll average of Peltola +2.6. DDHQ takes off 5.6 in Kansas, 3.6 in Ohio, 1.7 in South Carolina, 1.3 in Texas and 1 in Alaska, and adds 0.4 in Iowa. FiftyPlusOne takes off 1.7 in Ohio, 1 in Kansas, 0.9 in Texas and 0.5 in South Carolina, and adds 0.3 in Iowa and 0.1 in Alaska. South Carolina moved most: Kalshi went from 20.5% on October 24 and 20% on October 25 to 24% today, with the poll average unchanged at Graham +2.1, so its markdown went from 3.3 points to 2.5. FiftyPlusOne's October 26 reading has Ohio at 62.7% from 64.5% and Kansas at 48.7% from 51.2%, against poll averages of Brown +3.8 and Hamilton +0.8. Kalshi is at 67.5% in Ohio, 64.5% in Texas (poll average Talarico +2.3) and 41.5% in Iowa (Hinson +0.1). Against the 2-to-5-point band in the record, the market sits inside it in South Carolina and Kansas and under it in Iowa, Ohio and Texas; the October 3 call rested on four seats inside the band and today there are two. DDHQ sits inside it in Ohio, under it in South Carolina, Texas and Iowa and above it in Kansas; FiftyPlusOne sits under it in all six. DDHQ's numbers are dated October 2.

• The record: Republican-state Senate polls overstated the Democrat in 17 of 19 midterm races since 2014, by 5.3 points on average, and by 2 to 3 points in the contested races of 2018 and 2022.
• Base rates: out-party challengers have beaten an incumbent of the president's party in a state this red in 2 of 37 midterm races since 2006; open seats went 2 of 8.
• Alaska has votes behind its premium: Peltola out-polled Sullivan by 8 in the August primary, and the newest poll (New York Times/Siena, September 24 to October 1) has her up 50 to 43. Its Senate polls missed the other way in 2020, understating Sullivan's margin by about 8 points. Texas has only polls, and its final averages overstated the Democrat by 3 to 4.5 in the last two cycles.
• A third model, read once. Silver Bulletin's Deluxe forecast (October 4, subscriber page, not a board source) publishes projected margins, so its markdown can be read directly: 2.7 points off its own poll average in South Carolina and 2.1 in Kansas, inside the 2-to-5-point band; 0.4 off in Ohio, nothing in Iowa and 0.3 added in Texas, under it. Its South Carolina number is 19.8%, nearer the market's 14.5% than FiftyPlusOne's 36.1% that day. In Alaska it has Peltola at 62.9% on a 3.1-point first-choice lead, between the other two models and 11 points under the market; two other Republicans hold 4.2 points of first-choice vote in its projection, which under ranked-choice counting may be why the lead converts to a lower probability there than in any other tracked seat.