Set any Senate race to a winner and watch the odds of the three outcomes update. Races left on Model keep their forecast probability; a shared national polling error ties them together. Election day: Tue 3 Nov 2026.
Because every race that decides control sits inside that margin, and a polling miss moves them all together. The six Republican-held Senate seats Democrats are counting on show leads of 1.4 to 3 points (Texas +1.4, Alaska +1.8, Kansas +2.6, Maine +2.6, Ohio +3.0) and Iowa is tied. A 5-point national miss toward Republicans turns every one of those into a Republican win on the same night, so Democrats stay at 47–49 seats instead of reaching 51.
The House is no safer than it looks. Redistricting in Texas, Florida, Ohio and five other states cost Democrats about nine seats before a vote was cast, so an 8.7-point generic-ballot lead translates to roughly 236 seats, not the 250-plus it would have meant in 2018. At about 6.3 seats per point, the majority line of 218 is only 2.9 points of polling error away. A 3-point miss makes the House a coin flip; a 5-point miss puts it at about 205 Democratic seats and a Republican hold.
That is the whole story of the three scenarios: polls right or wrong by two points, Democrats sweep; wrong by three or four, Democrats take the House but not the Senate; wrong by five, Republicans keep both. The miss has happened before with Trump on the ballot (3 points in 2016, 4 in 2020) and never in a midterm since 1946, which is why the models put it near 10% rather than near zero.