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Plurality voting

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The first-past-the-post electoral system is a voting system for single-member districts, variously called first-past-the-post (FPTP or FPP), winner-take-all, plurality voting, or relative majority. In political science, it is known as Single-Member District Plurality or SMDP. This system is in use at all levels of politics; it is very common in former British colonies. For a thorough list, see below.

Procedures

Each voter selects one candidate. All votes are counted and the candidate or option with the most votes is the winner.

An example

Tennessee and its four major cities: Memphis in the far west; Nashville in the center; Chattanooga in the east; and Knoxville in the far northeast

Suppose that Tennessee is holding an election on the location of its capital. The population is concentrated around four major cities. All voters want the capital to be as close to them as possible. The options are:

  • Memphis, the largest city, but far from the others (42% of voters)
  • Nashville, near the center of the state (26% of voters)
  • Chattanooga, somewhat east (15% of voters)
  • Knoxville, far to the northeast (17% of voters)

The preferences of each region's voters are:

42% of voters
Far-West 		26% of voters
Center 		15% of voters
Center-East 		17% of voters
Far-East
  1. Memphis
  2. Nashville
  3. Chattanooga
  4. Knoxville
  1. Nashville
  2. Chattanooga
  3. Knoxville
  4. Memphis
  1. Chattanooga
  2. Knoxville
  3. Nashville
  4. Memphis
  1. Knoxville
  2. Chattanooga
  3. Nashville
  4. Memphis


If voting follows sincere preferences, Memphis is selected with the most votes. Note that this system does not require that the winner have a majority, but only a plurality. That is, Memphis wins because it has the most votes, even though more than half of the voters preferred another option.

Potential for tactical voting

First-past-the-post encourages the tactical voting technique known as "compromising": voters are encouraged to vote for one of the two options most likely to win, even if it is not their most preferred option. In the above example, voters from Chattanooga and Knoxville may "compromise" by voting for Nashville, which they prefer to Memphis.

If enough voters vote using this tactic, the first-past-the-post system becomes a form of runoff voting where the first round is held in the court of public opinion.

Anomalous results

An interesting anomaly in the results of this system arose in the Canadian federal election of 1926 for the province of Manitoba. The province was entitled to 17 seats in that election. The percentage of votes received across the province were

  • Conservatives 42.2%
  • Labour Progressives 19.5%
  • Liberals 18.4%
  • Progressives 11.2%
  • Labour 8.7%

The apportionment of seats however was

  • Conservatives 0
  • Labour Progressives 7
  • Liberals 4
  • Progressives 4
  • Labour 2

The Conservatives clearly had the largest number of votes across the province, but received no seats at all. The other parties were able to have success by having concentrated support in particular constituencies, and by not running candidates in others.

Duverger's law

Because of these anomalies and the tactical-voting tendencies, Duverger's law predicts that constituencies that use first-past-the-post systems will become two-party systems.

Where it's used

Countries that use this system to elect the lower or only house of their legislature:

Bahamas -- Bangladesh -- Barbados -- Belize -- Botswana -- Canada -- Dominica -- The Gambia -- Grenada -- Jamaica -- Federated States of Micronesia -- Nepal -- Papua New Guinea -- Saint Kitts and Nevis -- Saint Lucia -- Saint Vincent and the Grenadines -- Samoa -- Solomon Islands -- Trinidad and Tobago -- United Kingdom (Westminster elections) -- United States -- Zambia

see Table of voting systems by nation

The first past the post election system is used in the Republic of China on Taiwan for executive offices such as county magistrates, mayors, and the president, but not for legislative seats which used the single non-transferable vote system. This has produced an interesting party structure in which there are two broad coalitions of parties which cooperate in executive elections but which compete internally in legislative elections.

Source: Making Votes Count, Gary Cox (1997)

External links