Rizon2026 midterms: House and Senate seats as one number
On Oct 29, 2026, seat buckets on Polymarket and Kalshi implied about 196.6 House seats and 48 Senate seats for Republicans, and a D+9.3 national House vote.
Short answer: Five days before the Nov 3, 2026 midterms, the seat buckets on Polymarket and Kalshi implied a median of about 196.6 House seats for Republicans (196.7 from Polymarket's 10 buckets, 196.6 from Kalshi's 11) and 48 Senate seats, and a national House vote of about D+9.3. On Polymarket, Democrats to win the House traded at 92.5¢ and to win the Senate at 67.5¢. Rizon quotes each count as one book of strikes on half-seats, 196.5 or 48.5, and the vote margin in tenths of a point, Higher or Lower at 2×.
Control markets answer one yes-or-no question: who wins the chamber. The seat count answers by how much, and it's the number the bucket markets split up. This post gathers the prices on Oct 29, 2026 (recorded 08:05–08:40 UTC), the medians they imply, and the same numbers as one book each.
Control and the count
| Chamber | Democrats on Polymarket (¢) | Democrats on Kalshi (¢) |
|---|---|---|
| House | 92.5 | 91.1 |
| Senate | 67.5 | 66.5 |
Polymarket's balance-of-power market had a Democratic sweep at 66.5¢, a Republican Senate with a Democratic House at 27.5¢, a Republican sweep at 6.5¢ and a Democratic Senate with a Republican House at 0.85¢. The current Senate, per the congress-legislators data on Oct 29, is 53 Republicans, 45 Democrats and 2 independents.
House seats: Republicans
Polymarket's Republican House seats market ($0.37M traded across its 10 buckets, plus $6K in a separate lower-brackets event):
| Republican seats | Bid (¢) | Ask (¢) | Mid (¢) | Volume ($K) |
|---|---|---|---|---|
| Under 190 | 33 | 34 | 33.5 | 65 |
| 190–194 | 12 | 14 | 13 | 21 |
| 195–199 | 13 | 15 | 14 | 39 |
| 200–204 | 12.6 | 14.4 | 13.5 | 30 |
| 205–209 | 12.9 | 15.1 | 14 | 52 |
| 210–214 | 3.4 | 4.0 | 3.7 | 20 |
| 215–219 | 4.6 | 7.3 | 5.95 | 17 |
| 220–224 | 2.7 | 3.8 | 3.25 | 65 |
| 225–229 | 0.8 | 1.6 | 1.2 | 27 |
| 230 or more | 0.2 | 0.3 | 0.25 | 33 |
Kalshi's KXRHOUSESEATS-27 is the deeper market (5.9M contracts traded; its Democratic twin KXDHOUSESEATS-27, 4.5M):
| Republican seats | Bid (¢) | Ask (¢) | Volume (K contracts) |
|---|---|---|---|
| Under 193 | 39 | 40 | 1,021 |
| 193–197 | 15 | 16 | 379 |
| 198–202 | 15 | 16 | 310 |
| 203–207 | 8.1 | 9.7 | 329 |
| 208–212 | 6.0 | 7.0 | 319 |
| 213–217 | 2.9 | 3.8 | 416 |
| 218–222 | 5.4 | 5.7 | 778 |
| 223–227 | 2.8 | 3.2 | 682 |
| 228–232 | 1.0 | 1.7 | 623 |
| 233–237 | 0.2 | 1.0 | 503 |
| Over 237 | 1.4 | 1.7 | 547 |
Normalise each market's mids, find where the running total crosses one half, and interpolate inside that bucket: 196.7 on Polymarket and 196.6 on Kalshi. No bucket on either venue had a mid price above 40¢. Kalshi's Democratic-seat ladder implies 239.5 Democratic seats.
Senate seats: Republicans
Polymarket's Republican Senate seats market ($4.08M traded):
| Republican seats | Bid (¢) | Ask (¢) | Mid (¢) | Volume ($K) |
|---|---|---|---|---|
| 47 or fewer | 38 | 39 | 38.5 | 437 |
| 48 | 15 | 16 | 15.5 | 167 |
| 49 | 11 | 14 | 12.5 | 131 |
| 50 | 12 | 13 | 12.5 | 178 |
| 51 | 8 | 9 | 8.5 | 320 |
| 52 | 6.1 | 6.2 | 6.15 | 646 |
| 53 | 5.4 | 6.0 | 5.7 | 389 |
| 54 | 1.4 | 1.5 | 1.45 | 839 |
| 55 | 0.1 | 0.2 | 0.15 | 474 |
| 56 | 0.1 | 0.3 | 0.2 | 257 |
| 57 or more | 0.5 | 0.6 | 0.55 | 237 |
The median is 48 seats on both venues (Kalshi lists Democratic seats, with the median at 52). As one number, the 50/50 strike is 48.5: Higher means 49 or more, about 47% on these prices. A thin lower-brackets event ($13K) put 47 or fewer at about 45% rather than 38%.
The national House vote
Both venues sell the Democratic-minus-Republican margin of the national House vote in 2-point buckets, with open-ended tails:
| Margin, D − R (points) | Polymarket bid (¢) | Polymarket ask (¢) | Kalshi bid (¢) | Kalshi ask (¢) |
|---|---|---|---|---|
| 6 to 8 | 15 | 17 | 14 | 15 |
| 8 to 10 | 26 | 29 | 26 | 27 |
| 10 to 12 | 22 | 23 | 22 | 23 |
| 12 to 14 | 11.1 | 13.1 | 13 | 14 |
(The middle buckets only; Polymarket lists 13, Kalshi 10.) The medians: D+9.2 on Polymarket and D+9.5 on Kalshi, about D+9.3. The result comes from the Clerk of the House's election statistics, months after the vote.
The same numbers on Rizon
| HOUSE-R-2026 | SENATE-R-2026 | HOUSE-VOTE-2026 | |
|---|---|---|---|
| The number | Republican House seats won for the 120th Congress | Republican Senate seats in the 120th Congress | D% − R% of all valid House votes in the 50 states |
| Counting | Runoffs included; independents who caucus with the party count | Uncontested seats count for the holder; caucusing independents count | Delegates excluded |
| Strikes | Half-seats (196.5) | Half-seats (48.5) | Every 0.1 point on .05 (D+9.25) |
| Trading stops | When every race is called (Rizon halts it) | When every race is called | When the Clerk publishes |
| Settles on | Official state results and AP calls | Official state results and AP calls | The Clerk of the House's statistics |
| Expiry (UTC) | Jan 5, 2027, 04:59 | Jan 5, 2027, 04:59 | Jul 1, 2027, 03:59 |
The seat markets follow Polymarket's counting rules, and their expiry is Polymarket's deadline for independents to declare a caucus (Jan 4, 2027, 11:59 PM ET); Rizon halts them once every race is called and resolves them from official results and AP calls. Each is one book: House, Senate, popular vote. A view like "Republicans win 200 or more House seats" is Higher than 199.5, one contract, where on Polymarket it's seven buckets (or the No side of the other three).
When the numbers will be known
- Nov 1: US daylight time ends.
- Nov 3: Election day. The first polls close at 23:00 UTC (6 PM ET, in parts of Indiana and Kentucky); the last, in Alaska and Hawaii, at 06:00 UTC on Nov 4.
- Mid to late November: AP calls for the chambers. The House was called on Nov 13 in 2024 and Nov 16 in 2022, dates from memory that we haven't re-verified.
- December: State certifications, and any Georgia runoff (date not verified).
- Jan 3, 2027: The 120th Congress convenes.
- Jan 4, 2027: Polymarket's deadline for independents' caucus intent.
- Feb 1, 2027: Kalshi's seat markets settle on the seats held that day.
- By Jun 30, 2027: The Clerk's popular-vote statistics, Polymarket's deadline for its margin market.
FAQ
How many House seats will Republicans win in 2026, according to prediction markets?
On Oct 29, 2026, Polymarket's and Kalshi's seat buckets implied a median of about 196.6 Republican House seats (196.7 and 196.6), with Democrats to win the House at 92.5¢ on Polymarket.
How many Senate seats will Republicans have?
The buckets implied a median of 48 of 100 on both Polymarket and Kalshi on Oct 29, 2026, with Democrats to win the Senate at 67.5¢ on Polymarket. Republicans hold 53 seats now.
What does D+9.3 mean?
That the median expectation for the national House vote was Democrats ahead by about 9.3 percentage points of all valid votes for House candidates in the 50 states, between Polymarket's D+9.2 and Kalshi's D+9.5 on Oct 29, 2026.
When will Rizon settle its seat markets?
Rizon halts each seat market once every race has been called and resolves it from official state results and AP calls; its expiry, Jan 5, 2027 at 04:59 UTC, is Polymarket's caucus deadline. The popular-vote market waits for the Clerk of the House's figures.
Why half-seat strikes?
A seat count is a whole number, so a strike at 196.5 can't be hit exactly: Higher is 197 or more, Lower is 196 or fewer, and no contract pushes.