General · EdgepediaSeptember 17, 20266 min read

Two-round system

The two-round system (TRS) is an electoral method in which voters cast a single vote for a candidate, and if no candidate wins an overall majority, defined as 50 percent plus one of the valid votes cast, a second round is held, typically between the two leading candidates¹. It belongs to the plurality-majority family of electoral systems, and majoritarian systems such as the Alternative Vote and the two-round system share the aim of ensuring that the winning candidate receives an absolute majority².

Key fact	Detail
Winning threshold	First round: 50 percent + 1 of valid votes; normally an absolute majority, although several countries use a different figure when electing a president¹^•³
Runoff participants	The two leading candidates from the first round¹
Presidential use	Since the global wave of democratization in the 1990s, the most common way of directly electing presidents¹
Countries (presidential)	France, Nigeria, Brazil, Indonesia, Kenya, Cote d'Ivoire, Senegal, Zambia (since 2016), among others¹
Legislative use	Used to elect 22 national legislatures; France uses a majority-plurality variant for its legislative elections³
Party-system effect	Lower barriers to entry for third parties or new political movements than plurality systems; encourages pre-electoral agreements between large and small parties¹^•⁴

How it works

All candidates appear on the first ballot. If one candidate receives a majority, that candidate is elected and no second round is needed⁵. If no candidate reaches the majority threshold, the two candidates with the most votes advance to a second round, or runoff, held at a later date¹^•⁵.

Variants differ in the qualifying rule and the second-round threshold. In French regional elections, lists qualify for the second round at a threshold of 12.5 percent of registered electors, and in the second round only a relative (plurality) majority is needed to win⁶. The International IDEA handbook distinguishes the standard majority-majority form from the majority-plurality variant, in which an absolute majority is required only in the first round³. Timing also varies by country: Iran's law requires the runoff between the top two vote getters to take place within one week of the first round⁷, while in Turkey's 2023 schedule the second round followed the first by two weeks⁸.

Where it is used

For presidential elections, the two-round system spread widely after the democratization wave of the 1990s and became the most common method of directly electing presidents worldwide¹. The IDEA handbook reports that two-round systems are used to elect 22 national legislatures as well³.

Recent examples show the system in operation. In North Macedonia's 2024 presidential contest, the runoff of a two-round contest began in April and concluded in May, running alongside a parliament elected in a single round⁹. In Peru's 2026 presidential election, none of 35 candidates secured an outright victory, sending the top two to a June runoff¹⁰. Portugal's January 2026 presidential ballot went to a second round for the first time since 1986, only the second such election since democracy began there in 1976¹¹. In the United States, the Constitution leaves states free to set runoff rules for congressional elections, and states usually hold runoffs when no candidate receives a majority in the first election⁵. Georgia and Louisiana are the two states that require a runoff in all general elections if no candidate achieves at least 50 percent of the vote¹².

Effects on parties and candidates

Compared with a single-round plurality system, the two-round system lowers the barriers to entry faced by third parties or new political movements, making the system more responsive to changing societal needs¹. Because the runoff does not reward a mere plurality in the first round, more serious candidates run than under first-past-the-post, a prediction political scientists trace to Maurice Duverger's work; the runoff system is traditionally grouped with proportional systems in this respect¹³. Two-round ballots also tend toward bipolarization of political life, or at least toward pre-electoral agreements between large and small parties⁴. A regression discontinuity study of Italian municipalities, where cities above 15,000 inhabitants elect mayors by runoff while smaller cities use a single round, confirmed predictions that runoffs increase the number of candidates and reduce policy volatility, and found that candidates' strategic responses explain a larger part of the effect¹⁴^•¹⁵.

The system also shapes voter behavior. Áron Kiss, a political scientist who studies strategic voting, proposed a method to identify strategic ('wasted vote') behavior using two-round elections in which the runoff features three candidates, exploiting Hungarian elections between 1990 and 2010; the analysis found evidence for increasing strategic voting in post-transition Hungary¹⁶. In the other direction, research cited in an IMF working paper finds that third-placed and lower candidates receive higher vote shares in two-round elections, suggesting voters behave less strategically when a second round gives their first-round vote a signaling role¹⁵.

Costs and criticisms

The runoff is a distinct election with its own campaign period, observation needs, and integrity risks¹⁷, and holding it adds delay, cost, and administrative complexity¹. In the United States, Georgia's runoff carries a contested history: it was introduced in 1963 by state representative Denmark Groover, an avowed segregationist, after he lost a 1958 race he blamed on Black "bloc voting," on the reasoning that a runoff would rally white voters around a white candidate and decrease the likelihood of an African American being elected¹².

Assessments of representation are mixed. FairVote's comparison of voting methods finds that two-round runoffs outperform plurality voting in electing politically representative groups of public officials, but that little evidence finds they improve election rates for women or people of color¹⁸.

Comparison with instant-runoff voting

Instant-runoff voting (IRV), also called ranked choice voting or the alternative vote, replaces the separate second election with a ranked ballot on which the weakest candidate is eliminated and those ballots are redistributed until one candidate has a majority¹⁹. Both are single-winner majority methods in the plurality-majority family, and electoral-system software treats plurality, two-round runoff, and single transferable vote as distinct implementable rules²⁰. IRV descends from the single transferable vote invented in the 1850s by Thomas Hare in England and Carl Andrae in Denmark²¹, while the two-round system keeps two physical trips to the polls but lets voters reconsider their choice with full knowledge of the field that survived the first round.

References

Topic: Encyclopedia › Society and history › Politics and government › Elections and representation › Electoral systems and principles › Voting systems › Plurality and majority systems › Two-round and runoff systems

Initially written Sep 17, 2026 · Reviewed: Sep 30, 2026; Oct 25, 2026 · Edited: Sep 30, 2026; Oct 25, 2026 · Last review: Oct 25, 2026

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