G. Elliott Morris, who ran FiveThirtyEight until ABC shuttered it last year, has issued his first big election forecast of the cycle. It’s very good news for the out party.
Today’s the day we’ve all been waiting for. If you’re reading this, that means we finished dotting our i’s and crossing our t’s and just published our shiny, state-of-the-art 2026 congressional election forecast over at FiftyPlusOne. 🎉
As of 6:00 AM Eastern on August 3, 2026, we give the Democrats an 85% chance to win the majority in the U.S. House of Representatives and a 55% chance to win control of the Senate (which we define as 51 seats or more, unless an independent wins in Nebraska, Montana, Idaho, or South Dakota — unlikely, but not impossible).
Given the thin GOP margin in the current House, the historical tradition of the party controlling the White House losing seats in the midterms, and President Trump’s horrific polling numbers, I’m actually surprised that the forecast there is only 85%.
Even with all of that, though, I’ve been of the view that the Republicans are likely to hold the Senate, simply because of which seats are up this cycle. With Vice President J.D. Vance able to break any ties, Democrats need to net four seats to get to 51 to have a majority. The most likely flip is North Carolina, which has no incumbent with the retirement of Republican Thom Tillis and popular former Democratic Governor Roy Cooper in the lead. Still, Democrats need to hold Georgia and pick up three more from Alaska, Maine, Michigan, and Ohio.
That their forecast has it more likely than not that the Democrats will take the Senate, then, is a bold prediction just three months out. But they’re quite confident:
Because our forecast simulates elections for both chambers in one unified model, we can also calculate the probabilities of either party controlling both chambers after Nov. Democrats win control of both the House and Senate in just over 50% of simulations, whereas Republicans prevail in less than 12%.
At the FiftyPlusOne site, Morris provides a detailed explanation of “How the FiftyPlusOne 2026 election model works.” The short version:
The FiftyPlusOne method for forecasting the House and Senate draws on existing journalistic approaches to election forecasting as well as the academic literature on Bayesian models and correlated election polling errors. Our forecast “model” is in fact four models — three models of (1) what the polls say, (2) what the historical fundamentals say, and (3) what professional race handicappers say, plus (4) an “ensemble” model that combines the out-of-sample forecasts from each component model according to how much each has erred against past elections. We can then use the historical error of the ensemble model to simulate the whole election many thousands of times to work out not just who is ahead, but how wrong polls and other predictors might be, and how the race would move if they are.
Formally, our approach is called Bayesian model stacking (we shied away from the most complex version, Bayesian hierarchical stacking, for lack of development time) and is rooted in academic work showing that combining predicted probability from competing models leads to better forecasts on out-of-sample data. While some election forecasters gather time series of predictors, ignore their uncertainty, and, for example, stick them in a weighted average, our model learns the weight it should put on each component forecast based on the total uncertainty each model has about the outcome of the election — including, in the case of the polling model, the role of factors such as partisan nonresponse.
On top of this insight, we add a step that calibrates the ensemble itself to account for how forecasting errors have been shared across similar states and districts over time.
There’s a lot more on the page for those interested in a deeper dive.
I was curious about how Morris’ predecessor at 538, founder Nate Silver, was looking at the election. His initial forecast release will be next week. Right now, all he has is generic ballots, and only the House numbers are above the paywall.
