Research
How the forecast works, in full
The 12 papers behind our Poland forecast (14,683 words): how far the polls have missed, how we correct them, the seat model and the tests.
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. Po polsku
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12 papers · about 15k words · Our method, in short · How the elections work · Data sources
Poland
- Forecasting the Sejm from imperfect polls: an overview The Poland section forecasts the next Sejm election with the rule used for Great Britain: take half the average past miss off today's polls, but only where that would have improved past forecasts made without knowing the result. Polish final polls fail that test and are taken as published, with the don't-knows removed. The seats depend on the 5% and 8% thresholds as much as on the votes, and on a line-up the parties have not yet agreed, so the forecast states its assumption and shows three others; our calculation reproduces every Sejm election since 2005. Because the President can veto laws, the forecast reports 276 seats as well as 231. This paper maps the other Poland papers.
- Measuring Polish polling error, 2001–2023 We measure the error of the final polls at the Sejm elections from 2001 to 2023, taken a few days before the vote because of the election silence: which polls count, how the don't-knows are removed, how lists that merged and split are measured, the error list by list and on the gap between the two largest lists, each pollster's record and the long view. The lists that became Trzecia Droga were understated at five of seven elections; the other lines' large misses changed direction, from the left's in 2001 and 2005 to KO's.
- Reading Polish polls: why they are not corrected The core methods paper for Poland. Taking off half the average past miss, with each election predicted from the others, was further out on average at the seven Sejm elections since 2001, so Polish polls are taken as published. Only Trzecia Droga's line was missed the same way each time; the others' large misses changed sign. We set out the test election by election, how the don't-knows are removed, what CBOS's declared vote offers, and the seat calculation that reproduces every election since 2005.
- From votes to seats: the Kodeks wyborczy We implement the Sejm's electoral law: 460 seats in 41 okręgi, national thresholds of 5% for party lists and 8% for coalitions, an exemption for national minorities, and D'Hondt in each okręg. Given each election's official okręg votes, the calculation reproduces every list's seats from 2005 to 2023. National polls reach the okręgi by proportional swing from 2023, with the parties that split from the 2023 lists sharing their parent's vote. We explain the last seats, the German minority in Opole and the pending reapportionment.
- Line-ups and thresholds: 5%, 8% and the Trzecia Droga question Polish seats depend on who runs with whom: a party list needs 5% of the national vote, a coalition list 8%, a national minority nothing. Several parties poll near those lines, and the parties of Trzecia Droga, which won 14.4% together in 2023, poll about 4% today. We set out the thresholds and the four line-ups the forecast shows: every party apart (the default), Trzecia Droga again, two government lists, and one joint list, which with the same votes give the governing coalition very different seat totals.
- The President's veto and the 276 line A Sejm majority is 231, but a presidential veto can be overridden only by three fifths of the votes, 276 when all 460 vote. President Nawrocki, in office until 2030, has vetoed more than twenty of the government's laws. The forecast reports, for every combination of parties, the chance of 231 and of 276, today and on polling day. We explain the rule, the combinations shown, the President's role in forming a government and what the forecast does not model.
- Simulating Polish polling error: where the chances come from Seat ranges, each list's chance of clearing its threshold and each combination's chance of 231 and 276 come from 2,000 simulated elections under the default line-up, each party moved by its typical final-poll miss scaled to its size today, the thresholds checked on the national result, and each okręg moved by a local factor. The thresholds make the results lopsided. Drawing the right-wing parties' errors independently makes their total more uncertain than the record suggests.
- From today to polling day in Poland We test the British pull-back towards the previous result on Polish polls at ten distances up to three years before the Sejm elections of 2011 to 2023. It helps: from two years out the previous result was closer than the polls, and the fitted curve beat the polls at seven of ten distances. The polling-day forecast moves today's shares about half-way back towards the 2023 results of the lists they descend from, which lifts Trzecia Droga's parties and lowers the right's splinters, and widens the ranges for the time left.
- If we're wrong: replaying past Polish polling misses on today's polls Nine readings of today's Polish polls: as they stand (also our projection, because the correction is off) and each Sejm election's final-poll miss since 2001 replayed in full, all through the same seat calculation and line-up. The replays move seats mostly through the thresholds: 2001 pushes Lewica under 5%, 2005 and 2019 push Rozwój Plus under it. We explain why every okręg changes under at least one replay.
- Rating Polish pollsters: accuracy, the lead and openness Each Polish pollster is rated out of 100 on the British scale. Every one is graded C, D or E: a poor Polish final poll misses by almost as much as the scale allows, so accuracy points are scarce, and openness separates the pollsters. CBOS scores full marks for openness and none for accuracy; Opinia24 has the highest score. We set out the evidence, the openness items, the don't-knows and why Polish grades cannot be compared with other countries'.
- The Polish data: results, maps, statistics, MPs and polls Where every number on the Polish pages comes from: the PKW's results by okręg for every Sejm election since 2001 and the presidential elections of 2020 and 2025, GUGiK's boundaries, GUS statistics, the Sejm's open data, and polls matched against the pollsters' or outlets' own pages or taken from Wikipedia's tables. How each was changed and checked, the lineage coding, CBOS's declared vote, the election silence, the licences and why the Sejm's photographs are not used.
- What we don't know yet: limitations of the Polish forecast Every known weakness of the Polish forecast in one place: the assumed line-up and the thresholds, a correction that fails while the polls still miss, old misses applied to new parties, proportional swing for the splinters, the pull-back for Trzecia Droga, independent errors, don't-knows, the seats per okręg, the President and second-hand polls. For each, how much it matters and what would change our mind.
