Glossary

What the words on this site mean here, with the numbers we actually use.

Election-day forecast

Our estimate of the result on 3 November, allowing for everything that can still change.

Combines polls, each district's or state's fundamentals (past results, demographics, economy, candidates, money) and the national environment, and widens the uncertainty for the time left before the election. This is the headline number on every page.

Nowcast

What the polls say if the election were held today. Not a prediction of November.

Built from polls alone, adjusted for each pollster's measured lean and for partisan sponsors. It answers a different question from the election-day forecast, so the two are never averaged or shown as one number.

Chance (win probability)

How often a side wins across tens of thousands of simulated elections.

A 70% chance means the side wins about 7 times in 10 elections like this one -- and loses 3. It is not a vote share and not a margin. Over many races, things we call 70% should happen about 70% of the time; the Accuracy page checks that against past elections.

80% range

The span the result falls inside in 8 of 10 simulations.

One time in ten the result comes in above the range and one time in ten below it. A wide range means a genuinely uncertain outcome, not a vague model.

Safe / Likely / Lean / Toss-up

Labels for a chance: Safe 95%+, Likely 85-95%, Lean 60-85%, Toss-up 40-60%.

The rating is a translation of the forecast's chance into words, computed the same way for every race; no one assigns it by judgment. Lean R means Republicans win 60-85% of simulations, and so on.

Research model

This chamber total has not yet passed our accuracy test against past elections.

Each race inside it has passed; the step that adds races into a chamber total has not yet been tested on 2016-2024 seat counts. The label comes off only when it passes.

Range for independents

Shown when an independent could win and has not said which party they would join.

Senate control depends on which party each senator organises with. Where an independent has made no commitment (Nebraska, Idaho, South Dakota, Montana in 2026), the low end assumes they do not side with Democrats and the high end that they do. We do not guess a person's choice.

Simple average

The plain mean margin of a race's polls in the last 30 days.

Every poll counts equally, whoever ran it or paid for it. Shown so the adjustment in the adjusted average is visible.

Adjusted average

The polls weighted by recency and size and corrected for pollster lean.

This is the nowcast's estimate of the race today. Pollsters that have historically leaned one way are corrected by their measured lean; polls paid for by party-aligned groups are discounted.

Partisan sponsor

A poll paid for by a party, campaign or party-aligned group.

Such polls are published more often when they are good news for the sponsor, so on average they lean toward them. They are kept, shown and flagged, and the adjusted average corrects for the lean.

National environment

How the country as a whole is leaning this year, in points.

Estimated from the generic congressional ballot, presidential approval and the economy, and checked against past midterms. It moves every race together, which is why seats are not independent coin flips.

Model change

A forecast moved because our method changed, not because anything happened.

When a new version of a model replaces an old one, its forecasts can differ. Those moves are listed separately so they are not mistaken for news.