Research
How the forecast works, in full
These papers set out every part of our method: what we measure, how we correct the polls, how votes become seats, how uncertain the result is, and what we have tested and rejected. Figures marked Live are computed from the database each time the page is built, so they always match the forecast.
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14 papers · about 54k words · Short summary of the method · How we adjust today's polls · Data sources
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Foundations
- Measuring polling error in England, 2015–2024 Final polls at the last four general elections understated the Conservatives in England at three of them and overstated UKIP, the Brexit Party and Reform at all four, while Labour's error changed sign. We define the error, show how the evidence was chosen and graded, and explain why the size of past misses, not their average direction, sets our uncertainty bands.
- From answers to headlines: the stage model of a published poll A published voting-intention figure is the end of a chain of steps (weighting, a turnout filter or weight, the handling of don't knows), and each pollster runs the chain differently. We store every poll's tables at each stage, derive England from the GB banner by one of four stated rules, check the arithmetic automatically, and find that at 2015–2024 final polls the answers before those steps missed in a steadier direction than the headlines did.
The method
- Correcting the raw answers: the method behind our projection Our projection starts from what poll respondents actually said, before each pollster's turnout and don't-know adjustments, and removes half of the average amount those raw answers have missed by in England since 2015. Tested on four elections, each predicted without its own result, it beat or matched the pollsters' published figures every time, but by modest margins, and it did not fix the large overstatement of Labour in 2024.
- Why we start from the raw answers rather than the published headline Correcting the pollsters' published figures by their own past miss has never beaten the uncorrected figures when each election is predicted from earlier ones, because the headline's error swings from election to election. The raw answers' error is larger but steadier, so it can be partly removed. Starting from the raw answers gave the best record of the variants we tested, but no variant, ours included, would have foreseen how far the polls overstated Labour in 2024.
- Lenses: reading the same polls several ways A lens is a vector of assumed polling errors subtracted from today's nation-level shares, followed by a rescale to 100. We show our projection beside the published figures, five past-miss scenarios, three pollster-based readings and the reader's own, and we do not average them, because only one of them has passed an out-of-sample test and the spread between the rest is the useful information.
Seats and uncertainty
- From votes to seats: swing models and their test We turn nation-level vote shares into 632 seat winners by moving each seat's 2024 result by its nation's change. Given the exact 2024 nation shares, uniform swing called 479 of 631 seats correctly from the notional 2019 result, ahead of a uniform–proportional blend (461) and proportional swing (445); all three badly under-called Labour, so the seat model, not the polls, is a major source of error in any projection.
- Simulating polling error: where the chances come from The site's seat ranges and probabilities come from 1,000 simulated elections. Each one replays one of the four real England polling-error patterns of 2015–2024, scaled by a random factor centred on zero, with Scotland and Wales taking their own errors from the same year, plus independent national and seat-level noise. Because errors are drawn as whole patterns, the simulation keeps the strong negative correlation between Conservative and Labour errors, but four patterns are a thin basis for calibration and some sources of error are left out.
- From today to polling day: how far polls move before an election Months or years before a British general election, the Conservatives, Labour and the Liberal Democrats have finished closer to their previous result than their polls suggested, while insurgent parties have not. Taking a little under two thirds of the big three's change since the last election at face value, and widening the uncertainty with the time left, beat the polls as they stood on average at every distance across the seven elections from 2001 to 2024 that the model uses.
- Scotland and Wales: sparse polls and no steady lean Scotland-only and Wales-only final polls have missed by roughly as much as England's since 2015, but not in the same direction from one election to the next. Correcting them by their own average past miss made them worse when each election was predicted from the others, so our projection leaves Scotland and Wales as polled, and their own error records are used only for the scenario lenses, the SNP and Plaid Cymru ranges and the simulation.
- MRPs and mega-polls: what they measure, how they have done, and how we treat them An MRP turns one very large poll into a seat count, and its total carries the error of the poll underneath: at the 2024 election every final MRP gave Labour more seats than it won, from 425 to 516 against 411. This paper sets out how MRPs work, their record since 2017, the 29 published since 2024 against our projection, why the October 2026 mega-poll's Labour majority comes from its vote shares, and how we use them.