Who controls the Senate after November?
50,000 simulated elections, seeding each race with its polling average, correlated polling error, and a prediction-market prior. Where the race stands today — current polling averages blended with prediction-market odds. A work in progress from Policy y Peaches.
Today’s climate (Republican president) implies a national D+5.8 margin. Measured against the 2024 House result, that is a uniform D+8.6 swing applied to every state’s fundamentals prior. It moves thinly-polled races the most.
Baseline: 44 safe D seats + 47 safe R seats; 9 competitive races simulated. Democrats need 51 seats for control.
Market odds also feed the per-race blend (weight 25% market / 75% polls).
- Polling margin
- D +7.9
- P(D), polls
- 94%
- P(D), blended
- 77%
- Polymarket
- 27%
- Kalshi
- —
- Polling margin
- D +8.3
- P(D), polls
- 95%
- P(D), blended
- 82%
- Polymarket
- 42%
- Kalshi
- —
- Polling margin
- D +7.3
- P(D), polls
- 93%
- P(D), blended
- 79%
- Polymarket
- 37%
- Kalshi
- —
- Polling margin
- D +8.5
- P(D), polls
- 95%
- P(D), blended
- 82%
- Polymarket
- 43%
- Kalshi
- —
- Polling margin
- D +13.1
- P(D), polls
- 99%
- P(D), blended
- 84%
- Polymarket
- 39%
- Kalshi
- —
- Polling margin
- D +0.8
- P(D), polls
- 57%
- P(D), blended
- 53%
- Polymarket
- 39%
- Kalshi
- —
- Polling margin
- D +1.7
- P(D), polls
- 65%
- P(D), blended
- 59%
- Polymarket
- 42%
- Kalshi
- —
- Polling margin
- R +0.5
- P(D), polls
- 45%
- P(D), blended
- 43%
- Polymarket
- 39%
- Kalshi
- —
- Polling margin
- R +1.5
- P(D), polls
- 36%
- P(D), blended
- 36%
- Polymarket
- —
- Kalshi
- —
How the simulation works
- Each race’s polling average margin is converted to a win probability using a fat-tailed Student-t error model: a national error (σ = 3) shared by every race plus an independent per-race error (σ = 4.5), sized to historical Senate polling misses. A shared tail shock allows unusually large misses to move several races together.
- The national midterm climate — the president’s approval and the generic congressional ballot — is folded into each race’s fundamentals prior as a uniform D+8.6 swing versus the 2024 House result. It mainly lifts thinly-polled seats; heavily polled races already price the climate in.
- Prediction-market odds are blended in at 25% weight — markets aggregate information polls miss, and the weight is a tunable model parameter.
- We then simulate 50,000 elections. The shared national error is what makes sweeps (all close races breaking one way) more likely than independent coin flips would suggest.
- This shows where the race stands today, given current polling and market prices. A work in progress from the team at Policy y Peaches — learn more here.
A work in progress from the team at Policy y Peaches. Learn more here.
Last updated: Aug 4, 2026, 11:07 PM