2026 Senate Forecast

The model is built to be simple enough to check by hand. Every number on this page comes from the data files listed below.

1. Polls. Only polls that finished in the last 30 days count. A poll's weight halves every 10 days, and bigger polls count more (by the square root of the sample size). If one pollster has several polls, they are averaged first so that one pollster can't take over the average. Likely-voter versions are used when a pollster released both.
2. Baseline. For races with a Democratic challenger, the polls are blended with a baseline: the state's 2024 presidential margin, minus the national 2024 margin, plus today's national generic ballot. With k polls, the polls get k ÷ (k + 2) of the weight. Races with an independent challenger (Idaho, Montana, Nebraska, South Dakota) use polls only, since a party baseline doesn't fit them.
3. Not everyone votes. The polls used are mostly likely-voter polls, which screen out people who probably won't vote. For election night, each state's expected vote is its voting-eligible population times the average of its 2018 and 2022 midterm turnout. That is how the map knows what share of the vote has been counted.
4. Chance to win. Each margin becomes a chance to win using a bell curve with a 5-point spread, or 7 points if the race has fewer than 3 polls.
5. Senate control. 10,000 simulated elections. Each one adds a shared national polling miss (3-point spread) plus a separate miss for each state (4 points, or 6 with fewer than 3 polls), so states can miss in the same direction like real polls do. 51 seats is a majority, and a 50–50 Senate goes to the Vice President's party (Republican). Independent winners are counted on their own.
6. Election night. Projected margin = (counted margin × share counted) + (pre-election margin × share still out). The spread shrinks as the count goes up. Some states count mail ballots first and others count them last, so early leads can swing either way. That's why the uncounted votes use the pre-election estimate instead of the current lead.
7. Calls. The model never calls a race. A race only shows as called after it's marked by hand from an AP or Decision Desk HQ call.

Known limits. The baseline ignores candidate quality and incumbency, which matters most in Maine. Alaska and Maine use ranked-choice voting, so the winner may not be known on election night. Georgia needs over 50% or it goes to a runoff on Dec 1. Expected vote totals are estimates, so "% counted" can run a little high or low.