229 Democrats
218 for Majority
Republicans 206
Election Day is Nov 3, 2026 (13 days away) · Projected: 229 D – 206 R
Dem Majority Prob 91.1%
National Margin D+4.5%
80% Interval 218–241
Voter Balls 0
Friend Network 0 Ties
OOS Model Record 198 / 204
Friends: 0 Formed +0 / Lost -0 Peer Persuaded: 0 CES β̄=0.533 Interactive LLM Pool →
T-300d Prior T-180d Spring T-90d Polls T-20d Today E-Day (Projected)
↓ 2026 Race Tables
Dem Lean D Undecided Lean R Rep Model Miss
Click a district or state for forecast details

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2026 Senate & House Swarm Forecast

Below are the full 2026 chamber projections and race-by-race tables aggregated from the county-level voter swarm. Each county's voting-age population is partitioned into demographic cells (Census CVAP × Cooperative Election Study), simulated across 5,000 correlated runs, and rolled up into states and redrawn 2026 congressional districts.

Senate 2026
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— Chance of a Democratic majority
House 2026
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— Chance of a Democratic majority
2024 Presidential Validation
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— P(Dem ≥ 270 EV)
2026 Senate Forecast Details · 100-Seat Chamber & All 35 Contested Races

Senate · 2026 Class 2 + Special Elections

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Full Senate composition (100 seats)

Faded squares represent seats not up for election in 2026; solid squares represent the 35 seats on the ballot, colored by the favored party in the simulation.

2026 Senate races on the ballot

StateIncumbentParty2024 Pres P(Dem)Rating Polls
2026 House Forecast Details · Seat Distribution Histogram & Competitive Districts

House · All 435 seats · 120th Congress

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Simulated Democratic seat distribution

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Competitive districts (projected margin within 10 points)

DistrictProjectedP(Dem) RatingPolls Counties
2024 Presidential Out-of-Sample Validation · State Projections from County Demographics

Presidential · Out-of-sample validation

State projections aggregated from county demographics

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States ordered by projected Democratic two-party vote share

StateProjectedActual P(Dem)RatingPolls EV
Historical Out-of-Sample Backtests (2012–2024) & Baseline Error Metrics

Out-of-sample evaluation

Historical backtests (2012–2024)

Each past election was evaluated strictly out of sample: the county prior and CES survey parameters were fit using only elections prior to the target year. For example, the 2016 backtest used only data from 2012 and earlier.

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Model accuracy & uncertainty

Baseline error metrics

While a voter-level simulation can output arbitrarily fine decimal numbers, its actual precision is bounded by its historical out-of-sample error. Across the four backtested presidential cycles (2012–2024), the model's mean absolute error (MAE) at the county level serves as the baseline uncertainty floor used to calibrate simulation intervals.

County MAE
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State MAE
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State Brier score
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Correct state calls
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Polled Senate races
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Polled House seats
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Counties modeled
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Counties omitted
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Curious about the Swarm equations, 2012–2024 backtests, or LLM voter dialogues?

Explore the mathematical roll-up sandbox, out-of-sample accuracy benchmarks, and 4-turn synthetic agent transcripts on our companion methodology page.

Math, Backtests & Agent Dialogues →
Generated by pipelines/swarm.py. Switch to the Monte Carlo Simulator, return to the 2026 Overview, read the Methodology & Past Elections Archive, read the Blog Post, or ☕ Buy Me a Coffee.
Required Data Attributions: MIT Election Data + Science Lab (MEDSL, CC BY 4.0) · Voting and Election Science Team (VEST, CC BY 4.0) · Harvard Election Data Archive (HEDA, CC BY) · Cooperative Election Study (CES, CC BY 4.0) · Heideman (2026) Redistricting boundary archive (CC BY 4.0) · OpenElections Project (CC BY 4.0) · UF Election Lab Early Voting Tracker (CC BY 4.0) · FiveThirtyEight Pollster Ratings archive (CC BY 4.0) · Wikipedia Contributors (CC BY-SA 4.0). Full license & citation details →