Democrats clear favourites for the House · Democrats slight favourites for the Senate
Le Millénaire · election on 3 November 2026 · 200,000 simulations per chamber · updated 3 October 2026
Chances of control on 3 November
435
House of Representatives
94.8%
Democratic chances
239.4
out of 435 · 90%: 217 to 264
100
Senate
57.3%
Democratic chances, allied independents included
50.9
out of 100 · 90%: 47 to 54
of which 18.4% only if newly elected independents (Achilles, Bodnar, Osborn, Bengs) sit with Democrats; 38.9% without them
36
Governors
27.5
Republican governorships expected out of 48 counted
20.5
90% D: 17 to 24 · Alaska and Maine not counted
Probabilities are conditional on a Democrat versus Republican contest in each race. Updated 3 October 2026.
How the election can play out
The four outcomes for Congress. The model measures each chamber; the link between them cannot be measured, hence an exact range for each outcome.
Democrats control both chambersHouse and Senate, allied independents included52.1% to 57.3%
Democratic House, Republican Senatedivided Congress37.5% to 42.7%
Republican House, Democratic Senatedivided Congress0.0% to 5.2%
Republicans keep both chambersthe status quo0.0% to 5.2%
How to read. The dark bar is the minimum guaranteed by each chamber's chances, the light bar the maximum possible. The Senate counts newly elected independents with the Democrats; without them, Democrats control the Senate in 38.9% of simulations.
How the chances have moved
One point per daily calculation. Points up to and including 1 October 2026 were recomputed afterwards with the current method and the polls whose fieldwork had closed by each date.
House, D chancesSenate, D + allied I chances
Democrats control both chambers: between 52.1% and 57.3%. The model does not measure the link between the two contests, so it gives an exact range rather than a single figure.
The electoral map
Chances of the Democratic side, or of the independent where they are the main challenger, state by state. Hover a state for its figures.
Independents: Achilles (Idaho), Bodnar (Montana), Osborn (Nebraska), Bengs (South Dakota), shaded by their chances. Alaska and Maine (governors): multi-candidate contests, not yet probabilized.
The House of Representatives
Distribution of Democratic seats over 200,000 simulations. Blue: Democratic majority (218 seats or more).
National generic ballot (likely voters): each dot is a poll published since June, as the Democratic minus Republican margin. The line is a descriptive 21-day rolling average. The model applies its own aggregation rule.
56 polls from 19 pollsters, 17 June 2026 to 28 September 2026. Value used by the model on 3 October 2026: Democrats +7.4 points. Sources: Decision Desk HQ, public Wikipedia tables.
The test on past elections
Each engine was replayed on past midterms, with only the data available at the test date.
Engine
Test
Error
Probabilities
House, national
2010, 2014, 2018 at day −60
1.46 points of Democratic share
error carried into the 200,000 simulations
House, districts
984 contests 2010-2018, out of sample
margin: RMSE 9.91 points (10.18 without finance)
Brier 0.062
Senate
out-of-sample validation, Common State file
margin: RMSE ≈ 7.70 points
Brier 0.046 · correct winner 92.4%
Governors
144 races 2010-2022, leave one year out
margin: RMSE 13.24 points
Brier 0.118
The generic ballot against the results
Midterm
Polls at day −45
Actual national vote
Gap
2006
+9.2
+8.0
−1.2
2010
−3.6
−6.8
−3.2
2014
−1.8
−5.7
−3.9
2018
+8.8
+8.6
−0.2
2022
+1.8
−2.7
−4.5
Democratic minus Republican margin, in points. Polls overstated Democrats in 5 of 5 midterms; the model does not correct this bias in advance (correction rejected out of sample), it builds it into its uncertainty. Sources: FiveThirtyEight average, Clerk of the House.
The 2024 election
The starting point: the Congress and governors elected in 2024.
House
D 215 · R 220
Senate
D 45 · I 2 · R 53
Governors
D 23 · R 27
220
Republican House seats
215
Democratic seats
+3
seats Democrats need to gain
+4
D + I seats to gain in the Senate
House: national vote 49.8% Republican, 47.2% Democratic. Senate after 2024: 53 Republicans, 45 Democrats, 2 independents who caucus with them. Sources: Wikipedia, from the Clerk of the House and official state returns.
How it works
A forecasting model is not one more poll. It gathers what can be measured: published polls, past results, incumbency, fundraising. From these it derives a distribution of possible outcomes, with their probability.
Three engines
House, Senate and governors each have their own engine, validated on past midterms. All start from the same national environment, the likely-voter generic ballot, recomputed daily.
Past polling errors
Polls missed in every midterm, most often in favour of Democrats. The model replays the size of these errors in both directions. It does not assume in advance that one side will be underestimated.
Two hundred thousand simulations
Each chamber is replayed 200,000 times, with a national error shared by every race and an error specific to each race. The probability shown is the share of simulations in which the event happens.
What remains outside the calculation
The link between House and Senate cannot be measured over four midterms: the page gives an exact range rather than a figure. Candidates outside the top two are bounded by the polls, and Alaska and Maine (governors) are not yet probabilized.
What the model measuresThree independent engines, validated out of sample on past midterms. House: each district's 2024 result, incumbency and the national generic ballot, with a national error calibrated on polling history. Senate: race polls (56%), state history and candidate profile (44%). Governors: structural formula (2024 presidential vote, national climate and an incumbent governor on the ballot); polls enter from 13 October, a horizon validated on four elections.
What it does not say yetChances are computed between Democrat and Republican, or between independent and Republican where the independent is the main challenger (Idaho, Montana, Nebraska, South Dakota). 14 districts (Louisiana, same-party runoffs) remain outside the full field. In the Senate, a third candidate's chance is bounded by the polls: below 0.5% in Alaska, Maine and Nebraska; at most: Montana 1.7% (Alani Bankhead, D). The joint House and Senate probability is given as an exact range: the dependence between the two contests cannot be measured from available history.
Sources
Polls: Decision Desk HQ and public Wikipedia tables. Past results: Clerk of the House, Federal Election Commission, MIT Election Data and Science Lab. Fundraising: Federal Election Commission public files. Candidates: state election authorities. Generic ballot history: FiveThirtyEight.
Credits
All rights belong to Le Millénaire SAS, 47 rue de Vivienne, 75002 Paris.
Model designed by Project director: William Thay Deputy project director: Sean Scull Political and data analysis: Matthieu Hocque / Pierre Clairé Data analysis, mathematics and validation: Florian Gérard-Mercier