Who controls Congress
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How the projection works
- What goes in. Each race starts from the 2024 results in that state or district (presidential margin, the 2024 House result where lines did not change, incumbency, and a Senate incumbent’s own past over-performance), all moved by one national number: the national House vote. That number comes from the generic-ballot polling average, corrected for how far those averages missed in 1998–2022. Where public Senate polls exist they are blended in by their measured accuracy. Expert ratings are shown for comparison and are not an input.
- Ranges are wide on purpose. Nearly all of the uncertainty is in the national vote, so races move together. The odds come from 20,000 simulated elections that share national, regional and state errors.
- On election night each official count is read as the final margin plus an error that is large when much of the vote is still out, and the counted races move every other race through the national and regional vote. The projections on this page then update every few minutes.
- Projections, not calls. A race is shown as decided only when the model’s probability is overwhelming or the result is official, and it is still labelled a projection. The official source is the authority for every final result.
- Built with AI. The model, the data pipeline and this page were built and are run with AI agents (including Anthropic’s Claude) under Spencer Cavendish Reed’s direction. It is an independent project, not a news organization’s decision desk.