Polity : Single-winner voting system

Single-winner voting system

  • A voting system in which a constituency elects a single person to some office.  Mainly there are three types of single-winner voting system. 1. One vote system, 2. Preferential or ranked systems, and 3. Rated systems

One vote systems - One vote at a time
  • In first-past-the-post (same as winner-takes-all, simple plurality, relative/simple majority) voting system the single winner is the person with the most votes; there is no requirement that the winner gain an absolute majority of votes.
  • Two-round (runoff) systems -If any candidate in the first round gains a majority of votes, then there is no second round; otherwise, the two highest-voted candidates of the first round compete in a two-candidate second round or all candidates above a certain threshold in the first round compete in a two-, three- or four-candidate second round.
  • Exhaustive ballot - Here if no candidate is supported by an overall majority of votes (50% of total votes) then the candidate with the fewest votes is eliminated and a further round of voting occurs. This process is repeated for as many rounds as necessary until one candidate has a majority. Thus several rounds of voting may be required until a candidate reaches a majority.It is used to elect the various party nominees for President of the United States, the host city of the Olympic Games, the host of the FIFA World Cup, and in the Papal Conclave.
  • Main advantages of single-winner voting system are Preservation of "one person, one vote" principle and it tends to promote two-party systems. It minimizes the influence of third parties and thus arguably keeps out extremists.
  • Main disadvantages are Tactical voting (a compromising technique in which Voters are pressured to vote for one of the two candidates they predict are most likely to win, even if their true preference is neither, because a vote for any other candidate will likely be wasted and have no impact on the final result), wasted votes (votes casted for losing candidates or votes casted for winning candidates in excess of the number required for victory) and Gerrymandering (practice that attempts to establish a political advantage for a particular party or group by manipulating geographic boundaries to create partisan, incumbent-protected areas)
Preferential systems (ranked voting) - voters rank candidates in order of relative preference.
  • In Instant-runoff voting (IRV), also known as the alternative vote (AV) and ranked choice voting, one winner is elected from a pool of candidates using preferential voting. Voters rank candidates in order of preference, and their ballots are counted as one vote for their first choice candidate. If a candidate secures a majority of votes cast, that candidate wins. Otherwise, the candidate with the fewest votes is eliminated. A new round of counting takes place, with each ballot counted as one vote for the advancing candidate who is ranked highest on that ballot. This process continues until the winning candidate receives a majority of the vote against the remaining candidates. The President of India and members of legislative councils in India are selected using this method.
  • Condorcet method is a voting system that will always elect the Condorcet winner; this is the candidate whom voters prefer to each other candidate, when compared to them one at a time. This candidate can be found by conducting a series of pairwise comparisons (For example, with 5 candidates there are 10 pairwise comparisons to be made.) It has different versions like Copeland's method, Kemeny–Young method, Schulze method, Ranked pairs Minimax etc
  • Coombs' method : If at any time one candidate is ranked first (among non-eliminated candidates) by an absolute majority of the voters, then this is the winner. As long as this is not the case, the candidate which is ranked last (again among non-eliminated candidates) by the most (or a plurality of) voters is eliminated. Conversely, under instant run-off voting the candidate ranked first (among non-eliminated candidates) by the fewest voters is eliminated.
  • Other preference voting systems are Bucklin voting (based on median ranking), and Borda count (based on points)
Rated Voting - Voters rate candidates.
  • Range voting - Also called as ratings summation, average voting, cardinal ratings, score voting, 0–99 voting, the score system etc.Here voters score each candidate, the scores are added up, and the candidate with the highest score wins.
  • Approval voting can be considered to be range voting with only two levels: approved (1) and disapproved (0).
  • Majority Judgment - Here Voters freely grade each candidate in one of several named ranks, for instance from "excellent" to "bad", and the candidate with the highest median grade is the winner.