Electoral systems



Electoral systems are methods of translating votes into seats in an assembly or political office.

All systems fall into four categories:

  • Majoritarian
  • Plurality
  • Proportional
  • Mixed/Hybrid
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Majoritarian Systems

  • These systems require the winning candidate to aquire a majority vote to win the seat
  • Used in single member constituencies
  • The Alternative Vote is an example of a majoritarian system
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Plurality Systems

  • The winner requires a plurality of votes (one more than their rival)
  • Used in single member constituencies
  • First Past the Post is an example of a plurality system


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Proportional Representation

  • This covers many systems that aim to keep a close fit between number of votes and number of seats
  • Electoral formulas work out the number of seats gained in multi member costituencies
  • The Single Transferable Vote and Regional List system are examples of proportional representation
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  • This combines elements of plurality, majoritarian and proportional representation into one system
  • Some MPs are elected in single member constituencies, others are elected in multi member constituencies
  • The additional member system is an example of a mixed system
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WHAT IS IT? - An electoral system where the person with the most number of votes is elected. Victory is achieved by having one more vote than other contenders – it is also called a plurality system.

WHAT IS IT USED FOR? - UK general elections and by-elections and local council elections in England and Wales.

HOW DOES IT WORK? - On election day, voters receive a ballot paper with a list of candidates. As only one MP will represent the area, each party only stands one candidate to chose from. Voters usually put a cross next to their favourite candidate. But if they think their favourite has a low chance of winning, they may put a cross next to one they like the most with a better chance of winning.


Simple to use, both when voting and when working out the winner
Produces strong, stable Governments; 2010 Con-Lib is only post-war coalition
Prevents more extreme parties from gaining seats
Keeps effective and clear link between voter and their representative


Creates a 2 party system, favours Labour and the Conservatives
Smaller parties are under represented
Votes are wasted, causes lower turnouts
Encourages tactical voting
Winner may not have support from the majority of voters = less legitimacy

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WHAT IS IT? - A  majoritarian electoral system where voters number candidates in order of preference. 

WHAT IS IT USED FOR? - Labour party leadership elections and Australian house representative elections. 

HOW DOES IT WORK? - Rather than an X by one candidate as in First-Past-the-Post, the voter puts a ‘1’ by their first choice, a ‘2’ by their second choice, and so on until they either run out of candidates or no longer want to express any preferences. 1st preference votes are counted, if no one gains an overall majority the last place candidate is eliminated and their votes redistributed to the voters 2nd preference. This is repeated until a winner with a majority is produced.


The winner has the support of the majority of voters
The link between representative and constituency is retained


The winner is the least unpopular, not the most popular
Potentially less proportional than FPTP - If used in 1997 general election Labour would have a bigger majority and Lib Dems more seats than Cons
Potential for more extremist parties to gain seats

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WHAT IS IT? - A majoritarian system where the voter makes two choices (hence the term ‘supplementary’). 

WHAT IS IT USED FOR? - Elections for the London mayor and other elected mayors as well as police and crime commisioner elections in England and Wales.

HOW DOES IT WORK? - Each voter is allowed a 1st and 2nd preference vote. If one candidate obtains over 50% on the first vote then the contest is complete, if no candidate attains this level, all but the top two candidates are eliminated. Then the supplementary choices are re-distributed and whoever gets most votes from the remaining two, wins the seat. 


Broad support must be gained by the winner
Keeps extreme parties out
Simple and straightforward to use


The winning candidate does not need a majority
If used for general elections, it would deliever a disproportionate outcome

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WHAT IS IT? - A proportional election system in which the proportion of seats won is as close to the proportion of votes won as is possible. Voters vote for a party, not a candidate, and the party gets roughly the same proportion of seats as votes.

WHAT IS IT USED FOR? - To elect members of European Parliament from England, Scotland and Wales.

HOW DOES IT WORK? - Representatives are elected in large multi-member constituencies. Parties draw up a list of candidates in order of who they want elected. Seats are then allocated proportionally according to number of votes gained by each party or independent.


A high degree of proportionality, especially in larger regions
Parties can increase numbers of women and ethnic minority candidates


Parties can use lists to favour candidates that support the leadership
Weak link between representative and constituency
Voters can't vote for a favoured candidate.

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WHAT IS IT? - A proportional system that allows voters to rank their voting preferences in numerical order rather than simply having one voting choice.

WHAT IS IT USED FOR? -  The N.Ireland assembly, European parliament elections in N.Ireland and Scottish council elections.

HOW DOES IT WORK? -  Multi-member consituencies are used and voters number their choices preferentially. In order to obtain a seat, a candidate must obtain a quota. After the votes are cast, those with the least votes are eliminated and their votes transferred and those candidates with excess votes above the quota also have their votes transferred.


Only parties with 50% of the vote can form a government
Delivers proportional outcomes and ensures votes are of very similar value
Close correlation between votes and seats
Voters have wide choice of candidates, including ones from the same party


Likely to produce coalitions
Not fully proportional, particularly where small multi-member consituencies are used
Link between the member and voters may be weak in large multi member constituencies.

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WHAT IS IT? - A hybrid electoral system that has two components or elements

WHAT IS IT USED FOR? - The Scottish Parliament, welsh Assembly, Greater London Assembly (GLA)

HOW DOES IT WORK? - The voter makes two choices. Firstly, the voter selects a consituiency  representative on a simple plurality (FPTP) system then a second vote is apportioned to a party list for a second or ‘additional’ representative.


FPTP element keeps strong link between representative and constituency while retaining a fairer outcome
Votes are less likely to be wasted
Voters have lots of choice, they can essentially vote for 2 different parties


Smaller parties can still be under-represented
Assemblies have members with constituency responsibilities and members without them

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