How Democracies Work
Electoral Systems Explained: FPTP, PR, MMP and More
How votes are translated into seats varies enormously between democracies. This guide explains the main electoral systems and why they shape what polls can tell you.
12 min read · published February 12, 2026 · by the Democracy Pulse editorial team
Elections look superficially similar everywhere: voters cast ballots, ballots are counted, a winner emerges. The reality is almost the opposite. The rules that translate votes into seats — the electoral system — vary enormously between democracies, and those differences shape almost every interesting question about a political race. They determine which parties can realistically win seats, whether a polling lead translates into a governing majority, whether coalitions are routine or exceptional, and how much attention pollsters need to pay to the geographic distribution of support rather than the headline national number.
For anyone trying to read polls intelligently, ignoring the electoral system is the single biggest mistake you can make. A thirty-five percent lead in a single-member-plurality system usually means landslide. The same number in a strict proportional system means a likely coalition. Same poll, completely different story.
First Past the Post
First Past the Post (FPTP), or single-member plurality, is the oldest and simplest system. The country is divided into constituencies. Each constituency elects one representative. The candidate with the most votes wins, even if they are far short of a majority. The party that wins the most constituencies typically forms the government.
FPTP is used by the United Kingdom, the United States, Canada and India among others. Its strengths are simplicity, a clear local link between voter and representative, and a strong tendency to produce single-party majority governments. Its weaknesses are equally well-known: it discriminates heavily against parties whose support is geographically spread rather than concentrated, can produce results in which the party with the most national votes does not win the most seats, and tends to entrench two large parties at the expense of newer entrants.
For polling purposes, the consequence is that national vote share is only weakly informative about seat counts. A two-point national lead can produce a comfortable majority in one election and a hung parliament in another, depending on where the votes pile up. Constituency-level polling and uniform swing models are essential.
Proportional Representation
Proportional Representation (PR) is an umbrella term for systems designed to make the seat share of each party closely match its national or regional vote share. Most European democracies use some flavour of PR, as do New Zealand, Israel, and many Latin American and African countries.
The most common form is party-list PR. Voters cast ballots for a party (sometimes also choosing among that party's candidates), and seats are allocated within multi-member districts in proportion to each party's vote. A party that gets twenty-five percent of the vote in a district that elects ten members will, all else equal, get two or three seats.
The strengths of PR are that small and minority parties can win representation, the relationship between national vote share and national seat share is broadly fair, and voters who back losing candidates are not as comprehensively shut out as under FPTP. The weaknesses are that single-party majorities are rare, government formation is therefore usually a coalition negotiation that can take weeks or months, and the link between an individual MP and a specific local constituency is weaker.
Pollsters working in PR systems typically focus on national-level vote shares because they translate fairly directly into seat shares. The harder analytical question is which post-election coalitions are arithmetically possible, and which ones are politically plausible.
Mixed-Member Proportional
Mixed-Member Proportional (MMP), used by Germany and New Zealand among others, is a hybrid. Voters cast two ballots: one for a local constituency MP, elected by FPTP, and one for a party list. The list seats are then allocated to top up each party's constituency total so that the overall composition of the legislature is roughly proportional to the party-vote totals.
MMP is designed to combine the local representation of FPTP with the fairness of PR, and it broadly succeeds, at the cost of producing legislatures that vary in size and require an extra ballot. The system has a threshold — typically five percent — that a party must clear nationally to qualify for list seats, which prevents extreme fragmentation.
Single Transferable Vote
Single Transferable Vote (STV), used by Ireland, Malta, and the Australian Senate among others, is a candidate-centred form of proportional representation. Voters rank candidates in multi-member constituencies. Once a candidate reaches a quota of first-preference votes, they are elected, and their surplus votes are transferred to the next preference. Candidates with the fewest votes are eliminated and their votes redistributed.
STV produces broadly proportional outcomes while letting voters choose between individual candidates of the same party. It is complicated to count and complicated to poll: vote shares translate into seats only after multiple rounds of transfers, and knowing how supporters of one party will rank candidates of another is essential for forecasting.
Two-round runoffs
France's presidential and legislative elections, and many Latin American presidential contests, use two-round systems. In the first round, all candidates compete; if no candidate clears fifty percent (or another threshold), the top two — or, for some legislative variants, a small group of qualifying candidates — proceed to a runoff a week or two later.
Two-round systems guarantee that the winner has at least the support of a majority of voters in the runoff, but they introduce unique tactical considerations. First-round polls measure a completely different kind of choice from second-round polls: in the first round voters can express preferences, in the second they often vote against the candidate they like least. Polling averages need to handle the two rounds as separate phenomena.
Alternative Vote
Alternative Vote (AV), also called Instant Runoff Voting, is used for the Australian House of Representatives. Voters rank candidates in single-member constituencies. If no candidate has a majority of first preferences, the lowest-ranked candidate is eliminated and their votes redistributed to next preferences, repeated until somebody clears fifty percent.
AV preserves the local link of FPTP, eliminates much of the spoiler effect, and produces winners with majority support. It is proportional only inside each individual seat, not across the country, so the headline national vote share remains a poor guide to seat counts. Pollsters in AV systems typically report both primary vote (first-preference share) and a two-party-preferred figure (the projected share after preferences distribute).
Mixed and idiosyncratic systems
Many countries blend elements of these systems in idiosyncratic ways. Italy and Japan have used parallel systems combining FPTP and party-list PR without the corrective top-up that makes MMP proportional. Some countries layer regional and national tiers. Others impose minimum thresholds, majority bonuses, or gender quotas. Greece has used a bonus-seat system that hands extra seats to the largest party to encourage majority government. Ireland and Northern Ireland use STV in different ways.
The general lesson is that national vote shares mean different things in different systems. A poll showing a party at 35% is ambiguous on its own. In FPTP, that might be a comfortable majority. In strict PR, it is the largest single party but nowhere near a majority and almost certainly the lead negotiator in a coalition. Under a majority bonus, it might be exactly the threshold for a single-party government.
Why this matters for reading polls
Three practical implications for the careful reader:
- Don't equate vote share with seat share. Always think about the system before drawing conclusions about who will form the government.
- Pay attention to geography in FPTP and AV. A party leading nationally can still lose if its votes are concentrated in places it already wins easily.
- Pay attention to thresholds in PR and MMP. A party polling at four percent in a system with a five percent threshold is in genuine danger of winning zero seats. Small movements around the threshold can have huge consequences.
Electoral systems are not technicalities. They are the lens through which every poll has to be read.