The Senate tossup slate took in $9.29 million of trades over the latest day, more than any other live book on Polymarket, and the dearest exact map on that board still says Republicans win none of the seven states. Links to Polymarket are affiliate links, from which The Traders Spread may earn a commission at no cost to you. At 07:56 UTC on 31 October 2026, a gamma sort by 24-hour volume put the slate first and the balance-of-power book second at $2.78 million.
Senate tossup odds on the Iowa-and-Kansas map were 13.5 cents at the 07:54 UTC read, up 6.0 points on the day. The ticket pays only if Republicans win Iowa and Kansas and lose Alaska, Maine, Michigan, Ohio, and Texas. It traded $815,329 in that day, bid 13 cents, ask 14, last trade 14.
From the open to a 16-cent print
Orders started at 22:21 UTC on 26 October. The Iowa-and-Kansas Yes price then sat at 7.5 cents from 08:00 through 21:00 UTC on 30 October, printed 16 cents at 23:00 UTC, and was 13.5 cents again at 07:57 UTC on 31 October. Gamma's one-day change of 6.0 points matches the move off that 7.5-cent shelf to 13.5 cents, not the 16-cent print that failed to hold.
Where the other maps went
On the same 07:54 UTC read, Iowa only was 11.2 cents, up 3.0 points, on $679,473 of 24-hour volume. The seven-state sweep was 1.85 cents, down 4.05 points. The shutout ticket was 21.5 cents, down 3.0 points, and still the highest price. Kansas alone was 3.55 cents, down 2.35 points. Adding the mids that include each state puts Iowa at 65.5 cents and Michigan at 23.3 cents, and all 128 Yes prices sum to 110.6 cents, so those state totals run a little rich.
What the 29 October polls line up with
CNN published polls of likely voters at 5:00 a.m. ET on 29 October, about a day and a half before the 23:00 UTC spike. Fieldwork ran from 20 to 27 October in Michigan and Texas, and from 20 to 26 October in Kansas and Maine. Abdul El-Sayed led Mike Rogers 49 percent to 42 percent in Michigan (768 likely voters, margin of error 4.7 points). James Talarico led Ken Paxton 49 percent to 43 percent in Texas (923 likely voters, margin of error 4.2 points). Troy Jackson led Susan Collins 49 percent to 45 percent in Maine, and Adam Hamilton led Roger Marshall 49 percent to 45 percent in Kansas, each with a 4.5-point margin of error on 783 and 838 likely voters, while Iowa sat outside that set. The single-state Maine board is a separate contract from this slate.
Key facts
- 24-hour volume on the slate was $9.29 million, first on the active list, ahead of the balance-of-power book at $2.78 million. Source: Polymarket gamma-api, 31 October 2026, 07:56 UTC.
- The Iowa-and-Kansas map was 13.5 cents, up 6.0 points, bid 13, ask 14, last trade 14, on $815,329 of 24-hour volume. Source: Polymarket gamma-api, 31 October 2026, 07:54 UTC.
- That Yes price was 7.5 cents from 08:00 to 21:00 UTC on 30 October, 16 cents at 23:00 UTC, and 13.5 cents at 07:57 UTC on 31 October. Source: Polymarket CLOB prices-history, 31 October 2026.
- The shutout map was 21.5 cents, down 3.0 points, and still the highest price. The seven-state sweep was 1.85 cents, down 4.05 points. Source: Polymarket gamma-api, 31 October 2026, 07:54 UTC.
- Summing mids that include the state put Iowa at 65.5 cents and Michigan at 23.3 cents. All 128 Yes prices summed to 110.6 cents. Source: Polymarket gamma-api, 31 October 2026, 07:54 UTC.
What to watch
The slate covers Alaska, Iowa, Kansas, Maine, Michigan, the Ohio special election, and Texas. Associated Press, Fox News, and NBC calls resolve it on consensus, and a split goes to official certification. A state still unresolved on 31 March 2027 scores as a Republican loss under the rules. Trading runs through 23:59 UTC on 3 November 2026. The Iowa-and-Kansas price either holds near 13.5 cents or drifts toward the 7.5-cent shelf. Event liquidity was about $37.7 million at the 07:54 UTC read.
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Checklist
- The Iowa-and-Kansas Yes price belongs beside 13.5 cents and beside the 7.5-cent shelf from 30 October.
- The shutout ticket at 21.5 cents is what kept that map dearest against the two Iowa tickets.
- Slate volume at $9.29 million belongs beside the $2.78 million on the balance-of-power book.
- A one-cent twitch on Iowa and Kansas is the width of the 13-cent bid and the 14-cent ask.
Prices and polls here are a record, not a recommendation to buy or sell any contract.