The principle of plurality/majority systems is simple. After votes have been cast and totalled, those candidates or parties with the most votes are declared the winners (there may also be additional conditions). However, the way this is achieved in practice varies widely.
Five varieties of plurality/majority systems can be identified:
- First Past The Post (FPTP),
- Block Vote (BV),
- Party Block Vote(PBV),
- Alternative Vote (AV), and
- the Two-Round System (TRS).
In an FPTP system (sometimes known as a plurality single-member district system) the winner is the candidate with the most votes but not necessarily an absolute majority of the votes. When this system is used in multi-member districts, it becomes the Block Vote. Voters have as many votes as there are seats to be filled, and the highest-polling candidates fill the positions regardless of the percentage of the vote they achieve. This system—with the change that voters vote for party lists instead of individual candidates—becomes the Party Block Vote.
Majoritarian systems, such as the Alternative Vote and the Two-Round System, try to ensure that the winning candidate receives an absolute majority (i.e. over 50 per cent). Each system in essence makes use of voters’ second preferences to produce a winner with an absolute majority if one does not emerge from the first round of voting.
Variants of the Alternative Vote