Two-round system

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An example of Tow-round voting system. Re-run voting involves two rounds of voting. Only two candidates survive to the second round.

The two-round system (also known as the second ballot , runoff voting or ballotage or rerun) is a voting system used to elect a single winner where the voter casts a single vote for their chosen candidate. However, if no candidate receives the required number of votes (usually an absolute majority or 40–45% with a winning margin of 5–15%), then those candidates having less than a certain proportion of the votes, or all but the two candidates receiving the most votes, are eliminated, and a second round of voting is held.


The two-round system is known as a run-off election. Run-off voting is also sometimes used as a generic term to describe any system involving a number of rounds of voting, with eliminations after each round. By this broader definition the two-round system is not the only form of run-off voting, and others include the exhaustive ballot and instant run-off voting (also known as the alternative vote). However the subject of this article is the two-round system.

Voting and counting

In both rounds of an election conducted using runoff voting, the voter simply marks an "X" beside his/her favorite candidate. If no candidate has an absolute majority of votes (i.e. more than half) in the first round, then the two candidates with the most votes proceed to a second round, from which all others are excluded. In the second round, because there are only two candidates, one candidate will achieve an absolute majority. In the second round each voter is entirely free to change the candidate he votes for, even if his preferred candidate has not yet been eliminated but he has merely changed his mind.

Some variants of the two-round system use a different rule for choosing candidates for the second round, and allow more than two candidates to proceed to the second round. Under these systems it is sufficient for a candidate to receive a plurality of votes (i.e. more votes than anyone else) to be elected in the second round.


Imagine an election to choose which food to eat for dessert. There are 25 people having dessert and four candidates: Ice cream, Apple pie, Fruit and Celery. Runoff voting is used to find the winner.

Round 1: In the first round of voting each diner votes for the one candidate they most prefer. The results are as follows:

  • Ice cream: 10 votes
  • Apple pie: 6 votes
  • Fruit: 8 votes
  • Celery: 1 vote

Round 2: No candidate has an absolute majority of votes (in this election that would be 13) so the two candidates with the most votes, Ice cream and Fruit, proceed to a second round, while Apple pie and Celery are eliminated. Because their favorite candidates have been eliminated Apple pie and Celery supporters must now vote for one of the two remaining candidates. The sole Celery supporter is health conscious, so now gives his vote to Fruit. However Apple pie supporters are split: three prefer Ice cream and three vote for Fruit. Of those who supported Ice cream and Fruit in the first round no-one decides to change their vote. The results of the second round are therefore:

  • Ice cream: 13
  • Fruit: 12

Result: Ice cream now has an absolute majority so is declared the winner.


The intention of re-run voting is that the winning candidate will have the support of an absolute majority of voters. Under the "first past the post" system the candidate with most votes (a plurality) wins, even if they do not have an absolute majority (more than half) of votes. The two-round system tries to overcome this problem by permitting only two candidates in the second round, so that one must receive an absolute majority of votes.

Critics argue that the absolute majority obtained by the winner of re-run voting is an artificial one. As seen above, instant-re-run voting and the exhaustive ballot are two other voting systems that create an absolute majority for one candidate by eliminating weaker candidates over multiple rounds. However, as noted above in cases where there are three or more strong candidates, re-run voting will sometimes produce an absolute majority for a different winner than the candidate elected by the other two.

Advocates of Condorcet methods argue that a candidate can claim to have majority support only if they are the "Condorcet winner" – that is, the candidate who would beat every other candidate in a series of one-on-one elections. In re-run voting the winning candidate is only matched, one-on-one, with one of the other candidates. When a Condorcet winner exists, he does not necessarily win a re-run election due to insufficient support in the first round.

Re-run advocates counter that voters first preference is more important than lower preferences because that's where voters are putting the most effort of decision and that, unlike Condorcet methods, re-runs require a high showing among the full field of choices in addition to a strong showing in the final head-to-head competition. Condorcet methods can allow candidates to win who have minimal first-choice support and can win largely on the compromise appeal of being ranked second or third by more voters.

Practical implications

In large-scale public elections the two rounds of re-run voting are held on separate days, and so involve voters going to the polls twice. In smaller elections, such as those in assemblies or private organisations, it is sometimes possible to conduct both rounds in quick succession. However the fact that it involves two rounds means that, for large elections, re-run voting is more expensive than some other electoral systems. It may also lead to voter fatigue and a reduced turn-out in the second round. In every French presidential election since 1974, voter turnout actually increases in the second round. In re-run voting, the counting of votes in each round is simple and occurs in the same way as under the plurality system. Ranked voting systems, such as instant-re-run voting, involve a longer, more complicated count.

One of the strongest criticisms against the two-round voting system is the cost required to conduct two ballots. The two-round voting system also has the potential to cause political instability between the two rounds of voting, adding further to the economic impact of the two-round electoral system. Under an instant run-off ballot system there is only one round. It is alleged that the results of the election are known in days as opposed to months depending on the size of the electorate, but this is not always the case depending on the ability to count the rounds of the more complex instant runoff voting.

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