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This lesson examines the majoritarian electoral systems that have featured in UK politics, principally the Supplementary Vote (SV) and the Alternative Vote (AV), together with related systems such as the Two-Round System used elsewhere. Majoritarian systems occupy an important middle position in the study of electoral systems: they are designed to remedy one specific flaw of FPTP — the election of winners on a minority of the vote — without going as far as full proportional representation. Understanding them, and being able to place them accurately on the spectrum between plurality and proportional systems, is essential for Component 1 (Paper 1), and the recent history of SV in the UK provides valuable, exam-relevant material on how and why electoral rules are changed.
A majoritarian system is one designed to ensure that the winning candidate has the support of a majority of voters — more than 50% — rather than the mere plurality that suffices under FPTP. The central objection to FPTP at constituency level is that a candidate can be elected on, say, 35% of the vote when 65% of voters preferred someone else; majoritarian systems address this by using preferences to manufacture a majority for the winner.
It is vital to be precise about what majoritarian systems do and do not achieve. They tackle the legitimacy of the individual winner by ensuring they command majority support in their contest. They do not, however, make the overall result proportional. Like FPTP, majoritarian systems elect a single representative per contest, and the relationship between a party's national vote share and its seat share can remain just as distorted as under FPTP. This is the single most important point to grasp about this topic, and a very common source of error: majoritarian systems (SV, AV, the Two-Round System) are not proportional systems. A candidate who labels AV or SV "proportional" makes a serious factual mistake.
The reason for this is structural. Proportionality is a property of how an assembly as a whole is composed — how closely the spread of seats matches the spread of votes across the country. Majoritarian systems, by contrast, operate one single-member contest at a time and ask only whether the winner of that contest has majority backing. Improving the legitimacy of each individual winner does nothing, by itself, to bring the national balance of seats into line with the national balance of votes; a party can win majorities in the seats it takes while still being heavily over- or under-represented overall. The two questions — "did the winner of this seat command a majority?" and "does the legislature reflect the country?" — are simply different questions, and majoritarian systems answer only the first.
Majoritarian systems are also distinct from plurality systems (FPTP) on one side and proportional systems (STV, AMS, list) on the other. They sit between the two: more ambitious than FPTP about the legitimacy of the winner, but less ambitious than PR about the representativeness of the whole legislature. They are typically used to elect single office-holders — mayors, presidents — where the very nature of the office means only one person can win and proportionality is not even possible.
This last point deserves emphasis, because it explains why majoritarian systems have been used for the offices they have. When an electorate is choosing a single executive figure — a mayor, a Police and Crime Commissioner, a president — there is by definition only one prize, and the concept of "proportional representation" simply does not apply: one cannot share a single mayoralty among several parties in proportion to their votes. The relevant democratic question for such offices is therefore not "is the result proportional?" but "does the winner command majority support?" Majoritarian systems are tailored to exactly that question. This is also why the UK historically used SV for mayors and commissioners rather than for Parliament: for single-office elections the proportionality objection to FPTP is irrelevant, but the minority-winner objection is acute, and SV was designed to address it. Understanding this distinction between electing an assembly (where proportionality is possible and contested) and electing a single office (where it is not) is important for analysing why different systems are used for different elections.
The Supplementary Vote is a majoritarian system that was, until recently, a familiar feature of English elections for directly elected mayors and for Police and Crime Commissioners.
The defining feature of SV — and the source of much of its criticism — is that voters may express only two preferences, and that all but the top two candidates are eliminated in one go. A voter whose first and second preferences are both for candidates outside the top two has, in effect, no say in the final outcome; their vote does not carry through to the decisive stage. This is a key difference from the Alternative Vote, considered below, which allows voters to rank every candidate and eliminates candidates one at a time.
SV is sometimes described as a deliberately simplified, "voter-friendly" version of preferential voting: it captures much of the benefit of allowing a second choice while keeping the ballot and the count comparatively straightforward — there is only ever one redistribution, between two surviving candidates, rather than the cascade of successive eliminations that AV requires. Supporters of SV regarded this simplicity as a virtue for the high-profile, single-office elections to which it was applied, since the result could be reached and explained quickly. The trade-off, as the criticisms make clear, is that the simplification comes at the cost of completeness: limiting voters to two preferences is what allows ballots to be exhausted and what leaves the door open to a winner without true majority support.
The London mayoralty, while it used SV, repeatedly illustrated the system's central effect: a winner who fell short of a majority on first preferences could nonetheless cross the 50% line once second preferences were added.
| Year | Winner | First preferences | After redistribution |
|---|---|---|---|
| 2016 | Sadiq Khan (Labour) | 44.2% | 56.8% |
| 2021 | Sadiq Khan (Labour) | 40.0% | 55.2% |
In both contests the winner did not secure an outright majority of first preferences but was confirmed with majority support after the second preferences of eliminated candidates' voters were redistributed between the top two. This is precisely the outcome SV was designed to produce — a winner who, after preferences, commands the support of more than half of those whose ballots remained in play — and it is a useful concrete example to cite when explaining how majoritarian systems differ from FPTP.
| Advantage | Explanation |
|---|---|
| Broader winner legitimacy | The winner usually enjoys wider support than a bare FPTP plurality, having drawn on second preferences |
| Simplicity | Voters make only two straightforward choices, so the system is easier to use than fully preferential ones |
| Reduces tactical voting | Voters can mark a sincere first preference and use the second preference strategically, easing the dilemma FPTP creates |
| Single, clear winner | Like FPTP, SV produces one decisive winner, which suits the election of a single office-holder such as a mayor |
| Disadvantage | Explanation |
|---|---|
| Not proportional | SV is majoritarian; it does nothing to align overall seat shares with vote shares |
| Only two preferences | Voters cannot rank beyond two candidates, so support for all but the top two is lost once they are eliminated together |
| "Wasted" second preferences | A second preference for an eliminated candidate counts for nothing, so many ballots do not reach the final stage |
| Spoiled ballots | The two-column format confused some voters, producing comparatively high rates of rejected ballots |
| Still favours larger parties | The top two are almost always the major-party candidates, so smaller parties remain squeezed |
It is worth dwelling on the criticism that SV can still elect a candidate without true majority support. Because only the top two survive and only their second preferences count, a winner's final tally is a majority of the votes that remain in play, not necessarily a majority of all votes originally cast. Where many voters' first and second preferences are both eliminated, a substantial slice of the electorate exercises no influence over the decisive count. SV therefore mitigates, rather than wholly cures, the minority-winner problem of FPTP.
The spoiled-ballot problem also merits attention, because it featured in the government's case for abolition. SV uses a two-column ballot — one column for the first preference, one for the second — and some voters, particularly where the format was unfamiliar, marked it incorrectly, for example by placing two crosses in the first column or a single cross spanning both. Ballots marked in ways that breach the rules are rejected and do not count. Critics of FPTP's restoration argue that confusion of this kind is a reason to improve voter education and ballot design, not to abandon a system that delivers broader winner legitimacy; defenders of the change argue that a simpler ballot is itself a democratic good because it reduces the number of voters inadvertently disenfranchised by spoiling their papers. Either way, the episode shows how the administrative features of a system — not just its abstract fairness — feed into real political decisions about which system to use.
It is instructive to compare SV and AV directly, since they are often confused. Both are majoritarian and both use preferences, but they differ in two decisive respects. AV lets voters rank every candidate and eliminates candidates one at a time, so very few ballots are exhausted and the winner is highly likely to command a true majority. SV restricts voters to two preferences and eliminates all but the top two in a single step, so more ballots are exhausted and the winner's "majority" is only of the surviving votes. AV is therefore the more thorough majoritarian system, while SV trades some of that thoroughness for a simpler ballot. Recognising this distinction is exactly the kind of precise comparison that examiners reward, and it guards against the common error of treating the two systems as interchangeable.
AV is a fully preferential majoritarian system in single-member constituencies. It is the system that was put to the UK electorate in 2011 as a proposed replacement for FPTP at Westminster, and its rejection is one of the most important episodes in the modern history of electoral reform.
The crucial contrast with SV is twofold. First, AV allows voters to rank all candidates rather than just two. Second, AV eliminates candidates one by one, transferring votes at each stage, rather than removing all but the top two in a single step. As a result, AV is more likely than SV to produce a winner with genuine majority support, because far fewer ballots are exhausted before the decisive count.
A short worked example clarifies the mechanism. Imagine four candidates — A, B, C and D — where the first-preference shares are A 40%, B 31%, C 20% and D 9%. No candidate has reached 50%, so D, the lowest, is eliminated and D's ballots are redistributed to their second preferences. Suppose most of D's votes flow to C; C might now overtake B. The count then continues: the new lowest candidate is eliminated and their votes transferred, and so on, until one candidate passes 50%. The eventual winner need not be the candidate who led on first preferences: a candidate who is widely acceptable as a second or third choice can overtake an early leader who has more first preferences but less broad appeal. This is the feature that supporters praise — winners must build majority consent — and that critics attack, on the grounds that the "least-disliked" candidate may defeat the one with the most enthusiastic first-choice support.
In 2011 the UK held a nationwide referendum on whether to replace FPTP with AV for general elections. The referendum was a direct product of the 2010 hung parliament: holding it was part of the coalition agreement between the Conservatives, who opposed changing the system, and the Liberal Democrats, who wanted reform. The result was a decisive rejection of change.
| Result | Share |
|---|---|
| No (keep FPTP) | 67.9% |
| Yes (adopt AV) | 32.1% |
| Turnout | 42.2% |
The roughly two-to-one rejection of AV was a significant setback for the cause of electoral reform and is regularly cited by defenders of FPTP as evidence that the public does not want to change the system.
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