Edexcel A-Level Politics: Electoral Systems

Electoral systems are a core part of UK Politics, examined in Section A of Component 1 (Paper 1) on the Edexcel A-Level Politics (9PL0) specification. The topic asks you to understand how votes are turned into seats, why the choice of system matters enormously for the kind of government a country gets, and whether the UK should reform the way it elects MPs. This guide explains the four systems you must know -- First Past the Post, the Additional Member System, the Single Transferable Vote and the Supplementary Vote -- where each is used, their effects, and the outcome of the 2011 referendum on changing the Westminster system.

Where This Topic Sits

Each of the three 9PL0 papers lasts 2 hours, is worth 84 marks and counts for 33⅓% of the qualification, with assessment objectives weighted AO1 35% / AO2 35% / AO3 30%. Electoral systems appear in Section A of Paper 1, frequently through evaluative essays -- for example, whether First Past the Post should be replaced, or whether proportional systems produce better government. Because evaluation and analysis dominate the marks, you must compare systems and weigh trade-offs rather than simply describing how each one works.

The Four Systems You Must Know

System	Type	Used in the UK for
First Past the Post (FPTP)	Majoritarian/plurality	Westminster (UK general elections)
Additional Member System (AMS)	Hybrid/mixed	Scottish Parliament, Welsh Senedd, London Assembly
Single Transferable Vote (STV)	Proportional	Northern Ireland Assembly; Scottish local elections
Supplementary Vote (SV)	Majoritarian	Formerly elected mayors and Police and Crime Commissioners

First Past the Post (FPTP)

Under FPTP, the UK is divided into single-member constituencies and the candidate with the most votes (a plurality, not necessarily a majority) wins each seat. It is used for UK general elections to the House of Commons.

Its strengths are usually framed around effective government: it tends to produce single-party majorities and therefore strong, stable, accountable government; it is simple to understand; and it maintains a clear constituency link between an MP and a defined area. Its weaknesses centre on fairness: it is highly disproportional, so the share of seats a party wins can differ sharply from its share of votes; it produces large numbers of "wasted votes" and many safe seats; and it disadvantages smaller parties whose support is spread evenly across the country while it can reward those with geographically concentrated support.

Additional Member System (AMS)

AMS is a hybrid system that combines FPTP with a proportional element. Voters cast two votes: one for a constituency representative (elected by FPTP) and one for a party list. The list seats are allocated to correct the disproportionality of the constituency results, producing an overall outcome that is far more proportional. It is used for the Scottish Parliament, the Welsh Senedd and the London Assembly.

AMS is praised for combining a retained constituency link with broad proportionality, and for giving voters two votes. Critics note that it creates two categories of representative and that the party-list element strengthens party control over who is elected.

Single Transferable Vote (STV)

STV is a proportional system used in multi-member constituencies. Voters rank candidates in order of preference, and seats are filled using a quota; surplus votes from elected candidates and votes from eliminated candidates are transferred according to those preferences. It is used for the Northern Ireland Assembly and for Scottish local elections.

STV is highly proportional and gives voters a wide choice -- including between candidates of the same party. In Northern Ireland it is valued for enabling power-sharing across communities. Its drawbacks are the complexity of the counting process and the weaker link between a single representative and constituents, since each constituency has several members.

Supplementary Vote (SV)

SV is a majoritarian system in which voters mark a first and a second choice. If no candidate wins more than half of first-preference votes, all but the top two candidates are eliminated and the second preferences of the remaining ballots are redistributed to decide the winner. SV was formerly used to elect mayors (including the Mayor of London) and Police and Crime Commissioners, but it was replaced by First Past the Post for those contests from 2022. Knowing that SV is no longer used for these elections is an important up-to-date fact.

The 2011 AV Referendum

In 2011 the UK held a referendum on whether to replace First Past the Post for Westminster elections with the Alternative Vote (AV). The proposal was rejected, and FPTP was therefore retained for general elections. This result is essential evidence in any essay on electoral reform: it shows that, despite long-standing criticism of FPTP, the only nationwide opportunity to change it was turned down. You can use it to argue either that reform lacks public appetite or that the specific alternative on offer, rather than reform in principle, was what voters rejected.

It is worth being precise about what AV is and is not. AV is a majoritarian system, not a proportional one: voters rank candidates, and if no one wins more than half of first preferences, the lowest candidates are eliminated and their preferences redistributed until a winner has a majority. Because AV was the option on the ballot, the 2011 result tells us that voters declined this particular majoritarian alternative -- it was not a referendum on proportional representation as such. That distinction is exactly the sort of nuance that earns evaluation marks when you discuss whether the UK is likely to reform its voting system.

Referendums in the UK

Referendums are the principal form of direct democracy in the UK and they intersect closely with the electoral-systems topic. They have been used on major constitutional questions -- including devolution, electoral reform (the 2011 AV vote) and membership of the European Union. Supporters argue referendums confer strong legitimacy on big decisions and engage citizens directly; critics counter that they can reduce complex questions to a binary choice, expose minorities to majority will, and be heavily influenced by campaign resources and the media. Because Parliament remains sovereign, UK referendums are in strict legal terms advisory rather than binding, although in practice governments treat clear results as politically decisive.

Effects on Proportionality and Government

The heart of this topic is the trade-off between proportionality and strong government, and the table below is a useful framework for essays.

System	Proportionality	Typical effect on government
FPTP	Low	Often single-party majority; strong but can be disproportionate
AMS	High	Often coalition or minority; more representative
STV	High	Often coalition/power-sharing; broad choice
SV	Low (majoritarian)	Single winner with majority support in two-candidate run-off

The general pattern is that majoritarian systems (FPTP, SV) tend to produce decisive, single-winner outcomes but distort the relationship between votes and seats, while proportional and hybrid systems (AMS, STV) produce fairer representation but more often lead to coalition or minority government, which requires negotiation and compromise. Devolution provides a natural experiment: the Scottish Parliament, Senedd and Northern Ireland Assembly use more proportional systems and have frequently produced coalitions or power-sharing executives, in contrast to the usually single-party governments at Westminster.

Voting Behaviour and the Media

The companion strand to electoral systems is voting behaviour -- why people vote the way they do -- together with the influence of the media. Political scientists distinguish two broad families of explanation. Long-term factors shape voting over a lifetime and include social class, age, region, ethnicity and partisan attachment; historically, class was treated as the dominant influence, captured in the old idea that "class is the basis of British party politics". Short-term factors vary from one election to the next and include the salient issues of the day, the perceived competence of party leaders, the state of the economy, and the conduct of the campaign itself.

Most analysts now argue that class-based and partisan voting have weakened -- a long-term trend usually described as partisan dealignment and class dealignment -- making short-term factors and individual judgement more decisive than they once were. This makes elections less predictable and places greater weight on leadership image and campaign events.

The media sit alongside these factors. Newspapers, television and, increasingly, social media set the agenda by deciding which issues receive attention, frame how parties and leaders are perceived, and provide the main channel through which campaigns reach voters. Debate continues over how far the media actively change voters' minds as opposed to reinforcing views people already hold, and over the growing role of targeted online campaigning. When a question links electoral systems to outcomes, you can strengthen your answer by noting that the result of any election is shaped not only by the system that converts votes into seats but by these underlying patterns of voting behaviour and media influence.

Exam Technique

Electoral-systems essays are won on comparison and judgement. Whether the question asks if FPTP should be replaced or whether proportional systems are superior, structure your answer around the proportionality-versus-government trade-off, support each point with the right system and a real example (the Scottish Parliament for AMS, Northern Ireland for STV, the 2011 referendum for reform), and reach a clear, justified conclusion. Avoid simply explaining how each system works in turn without using that knowledge to answer the actual question -- and make sure your facts are current, including the move away from SV for mayors and PCCs.

Prepare with LearningBro

To master electoral systems and how they shape voting behaviour, work through LearningBro's dedicated course:

• Electoral Systems & Voting Behaviour -- covers FPTP, AMS, STV and SV, where each is used, their effects on proportionality and government, and the debate over electoral reform, with exam-style questions throughout.

The course uses spaced repetition and active recall so the systems, examples and reform arguments you revise stay firmly in your memory for exam day.