UK Polling Glossary A–Z
Definitions for every key term in UK political polling and elections — from approval rating to voting intention.
Approval Rating
A measure of how favourably the public views a politician, party, or institution. Usually expressed as a net approval rating: the percentage who approve minus the percentage who disapprove. A net approval of +10 means 10 percentage points more people approve than disapprove.
Leader Approval Ratings →By-Election
A parliamentary election held in a single constituency outside of a general election, triggered when a sitting MP dies, resigns, or is disqualified. By-elections are closely watched as a gauge of mid-term public opinion and are often won by opposition parties.
By-Elections Tracker →Constituency
One of the 650 geographic areas in the United Kingdom, each of which elects one Member of Parliament to the House of Commons. Constituency boundaries are periodically redrawn by the Boundary Commissions. Under FPTP, winning a constituency requires only a plurality of votes.
Constituency Data →Devolution
The transfer of certain legislative and executive powers from Westminster to devolved governments in Scotland, Wales and Northern Ireland. Scotland has the most extensive devolution, including powers over health, education, and aspects of tax. Devolved governments have their own separate elections and polling.
Scotland Polling →FPTP (First Past the Post)
The voting system used in UK General Elections. Each constituency elects one MP; the candidate with the most votes wins, regardless of whether they achieve a majority. FPTP tends to produce large seat majorities for parties with geographically concentrated support, and severely under-represents parties with spread-out support (e.g. Reform UK in 2024, which won 14% of the vote but only 5 seats).
FPTP Explained →General Election
A UK-wide vote in which all 650 parliamentary constituencies elect an MP simultaneously. The party that wins a majority of seats (326 or more) forms a government. The most recent General Election was on 4 July 2024, won by Labour with 412 seats. The next must be held by July 2029.
2024 GE Results →Hung Parliament
A situation where no single party wins an overall majority (326+ seats) in a General Election. This can lead to a minority government, a formal coalition, or a confidence-and-supply arrangement. The UK has had hung parliaments in 2010 and (briefly) after the 2017 election.
Seat Projection Calculator →IMD (Index of Multiple Deprivation)
An official measure of relative deprivation in small geographic areas across England, combining indicators for income, employment, health, education, housing, and services. It is used in research to understand how socioeconomic factors correlate with voting behaviour and polling results.
Issues Polling →MRP (Multi-Level Regression and Post-Stratification)
A statistical method that uses large national poll samples to produce constituency-level voting projections. MRP combines polling data with demographic information about each constituency to predict local outcomes far more accurately than simple national swing models. YouGov's MRP correctly predicted the scale of Labour's 2024 landslide.
MRP Polls →Net Approval
Approval rating minus disapproval rating, giving a single number that summarises public opinion of a political figure. A net approval of -35 means 35 percentage points more people disapprove than approve. Keir Starmer's net approval stood at approximately -35 in May 2026.
Leader Approval Tracker →Opinion Poll
A survey of a representative sample of the public designed to measure attitudes, voting intentions, or opinions on specific issues. UK political polls typically interview 1,000–2,000 people, weighted to reflect the demographics of the population. Major UK pollsters include YouGov, Ipsos, Survation, Redfield & Wilton, and More in Common.
All Pollsters →Poll of Polls
An average of multiple polls over a given time period, designed to smooth out the random sampling error of any individual poll. A poll of polls reduces the margin of error and gives a more stable picture of underlying public opinion. UKPollingData publishes a rolling poll of polls average.
Voting Intention Tracker →Proportional Representation (PR)
An alternative voting system in which parties win seats roughly proportional to their share of the vote nationally. Under PR, Reform UK's 14% in the 2024 election would have yielded around 90 seats instead of 5. PR is used in Scottish Parliament and Welsh Senedd elections, but not for Westminster.
FPTP vs PR Explainer →Swing
The shift in relative support between two parties from one election to the next, typically measured as the average of one party's gain and the other's loss. For example, if Labour falls from 34% to 18% and Reform UK rises from 14% to 28%, the swing from Labour to Reform is (14+14)/2 = 14 percentage points. Uniform national swing (UNS) assumes this swing is the same in every constituency.
Seat Calculator →VI (Voting Intention)
The core question in political polling: “If there were a General Election tomorrow, which party would you vote for?” VI polls measure current party support and are the primary input for seat forecasts. As of May 2026, UK VI polling shows Reform UK leading at 28%, Conservatives at 19%, Labour at 18%.
VI Tracker →