Wikipedia

Two-round system

For other types of runoff-voting systems, see Runoff voting (disambiguation).

The two-round system (TRS or 2RS), also called ballotage, top-two runoff, or two-round plurality (as originally termed in French[1]), is a single winner voting method. It is sometimes called plurality-runoff,[2] although this term can also be used for other, closely-related systems such as instant-runoff (or ranked-choice) voting or the exhaustive ballot (which typically produce similar results). It falls under the class of plurality-based voting rules, together with instant-runoff (or ranked-choice) and first-past-the-post (FPP).[3] In a two-round system, if no candidate receives a majority of the vote in the first round, the two candidates with the most votes in the first round proceed to a second round where all other candidates are excluded.[note 1] Both rounds are held under choose-one voting, where the voter marks a single favored candidate.

Countries by electoral system used to (directly) elect their head of state:
  First-past-the-post
  Two-round system
  Instant-runoff voting
Runoff voting ballots

The two-round system first emerged in France, and has since become the most common single-winner electoral system worldwide.[1][4] The two-round system is widely used in the election of legislative bodies and directly elected presidents. Despite this, the rule has received substantial criticism from social choice theorists, leading to the rise of electoral reform movements seeking to abolish it in France and elsewhere.

In the United States, the two-round system is called a jungle primary, and is used to elect most officials in Louisiana, Mississippi, and Georgia; California and Washington use a minor variant called a nonpartisan blanket primary. Alaska uses a two-round system that advances four candidates, with a ranked-choice runoff in the second round. In the rest of the country, the use of partisan primaries paired with the deeply entrenched two-party system is structurally similar to and often described as a de facto two-round system.[5][6][7]

Although advocates hoped the two-round method would elect more moderates and encourage turnout among independents, research has shown the method has little to no effect when compared to partisan primaries,[8][9] or with systems that only require a single round such as ranked-choice voting.[3][10][11] Research by social choice theorists has long identified all three rules as vulnerable to center squeeze, a kind of spoiler effect favoring extremists in crowded elections.[5][12][13]

Origins

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The French system of ballotage was first established as part of the reforms of the July Monarchy, with the term appearing in the Organic Decree of 2 February 1832 of the French government, which mandated a second-round election "when none of the candidates obtains an absolute majority".[14] The rule has since gained substantial popularity in South America, Eastern Europe, and Africa, where it is now the dominant system.[14]

Some variants of the two-round system use slightly different rules for eliminating candidates in the first round, allowing more than two candidates to proceed to the second round in some cases. Under such systems, it is sufficient for a candidate to receive a plurality of votes (more votes than anyone else) to be elected in the second round.

Example

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2002 French presidential election

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In the 2002 French presidential election, the two contenders described by the media as possible winners were Jacques Chirac and Lionel Jospin, who represented the largest two political parties in France at the time. However, 16 candidates were on the ballot, including Jean-Pierre Chevènement (5.33%) and Christiane Taubira (2.32%) from the Plural Left coalition of Jospin, who refused by excess of confidence[clarification needed] to dissuade them.[citation needed]

With the left vote divided among a number of candidates, a third contender, Jean-Marie Le Pen, unexpectedly obtained slightly more than Jospin in the first round:

  • Jacques Chirac (Centre-right, Gaullist): 19.88%
  • Jean-Marie Le Pen (Far-right, National Front): 16.86%
  • Lionel Jospin (Centre-left, Socialist): 16.18%

The other candidates received smaller percentages on the first round.

Because no candidate had obtained an absolute majority of the votes in the first round, the top two candidates went into the second round. Most supporters of the parties which did not get through to the second round (and Chirac's supporters) voted for Chirac, who won with a very large majority:

  • Jacques Chirac (Center-right, Gaullist): 82.21%
  • Jean-Marie Le Pen (Far-right, National Front): 17.79%

Despite the controversy over Jospin's early elimination, polls showed Chirac was preferred to Jospin by a majority of voters and that Chirac was the majority-preferred candidate, meaning the election was not spoiled.

2024 French legislative election

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French legislative elections allow more than two candidates to advance to the second round, leading to many triangular elections, such as in the 2024 French legislative election.[15] It is common for all but two candidates to withdraw from the second round (so they don't spoil the chances of another similar candidate) which makes the result similar to top-two two-round systems.

Variants

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Top-two primaries

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In the United States, the two-round system is used in Louisiana in place of traditional primary elections to choose each party's candidate. In this state, the first round is held on Election Day with runoffs occurring soon after. Georgia also uses the system for special elections.

Washington adopted a minor variant on the two-round system in a 2008 referendum, called the nonpartisan blanket primary or top-two primary. California approved the system in 2010, which was first used for the 36th congressional district special election in February 2011. The first election (the primary) is held before the general election in November and the top two candidates enter the general election. The general election is always held, even if a candidate gets over 50%.

Exhaustive ballot

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Main article: Exhaustive ballot

The exhaustive ballot (EB) is similar to the two-round system, but involves more rounds of voting rather than just two. If no candidate receives an absolute majority in the first round, the candidate with the fewest votes is eliminated. This continues until one candidate has an absolute majority. Because voters may have to cast votes several times, EB is not used in large-scale public elections. Instead it is used in smaller contests such as the election of the presiding officer of an assembly; one long-standing example of its use is in the United Kingdom, where local associations (LCAs) of the Conservative Party use EB to elect their prospective parliamentary candidates (PPCs). Exhaustive ballot is also used by FIFA and the International Olympic Committee to select hosts.

Instant-runoff voting

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Main article: Instant-runoff voting

Instant-runoff voting (IRV), like the exhaustive ballot, involves multiple reiterative counts in which the candidate with fewest votes is eliminated each time. Whilst the exhaustive ballot and the two-round system both involve voters casting a separate vote in each round, under instant-runoff, voters vote only once. This is possible because, rather than voting for only a single candidate, the voter ranks all of the candidates in order of preference. These preferences are then used to transfer the votes of those whose first preference has been eliminated during the course of the count. Because the two-round system and the exhaustive ballot involve separate rounds of voting, voters can use the results of one round to decide how they will vote in the next, whereas this is not possible under IRV. Because it is necessary to vote only once, IRV is used for elections in many places. For such as Australian general and state elections (called preferential voting). In the United States, it is known as ranked-choice voting and is used in a growing number of states and localities.

In Ireland it is known as the single transferable vote (STV) and is used for presidential elections and parliamentary elections. However, STV as applied in multi-member districts is a proportional voting system, not a majoritarian one; and candidates need only achieve a quota (or the highest remaining fraction of a quota), to be elected. STV is used in Northern Ireland, Malta, the Australian senate and various other jurisdictions in Australia.[16] It is often used for municipal elections in lieu of more party-based forms of proportional representation.

Contingent vote

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Main article: Contingent vote

The contingent or supplementary vote is a variant of instant-runoff voting that has been used in Queensland and was previously used in the United Kingdom to elect some mayors; it was ultimately abandoned as a result of its complex election administration[according to whom?]. Under the contingent vote, voters rank the top-two candidates. However it involves only two rounds of counting and uses the same rule for eliminating candidates as the two-round system. After the first round all but the two candidates with most votes are eliminated. Therefore, one candidate always achieves an absolute majority in the second round. Because of these similarities, the contingent vote tends to elect the same winner as the two-round system and instant-runoff voting.

Two-party-preferred vote

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Main article: Two-party-preferred vote

In Australian politics, the two-party-preferred vote (TPP or 2PP) is the result of the final round of an election or opinion poll after preferences have been distributed to the highest two candidates, who in some cases can be independents.[citation needed] For the purposes of TPP, the Liberal/National Coalition is usually considered a single party, with Labor being the other major party. Typically the TPP is expressed as the percentages of votes attracted by each of the two major parties, e.g. "Coalition 45%, Labor 55%", where the values include both primary votes and preferences. The TPP is an indicator of how much swing has been attained/is required to change the result, taking into consideration later preferences.

A two-party vote is used for elections to the Bhutanese National Assembly, where the first round selects two parties that are allowed to compete in the second round. Then, a second round is held using single-member districts with first-past-the-post.[17]

Compliance with voting method criteria

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Most of the mathematical criteria by which voting methods are compared were formulated for voters with ordinal preferences. Some methods, like approval voting, request information than cannot be unambiguously inferred from a single set of ordinal preferences. The two-round system is such a method, because the voters are not forced to vote according to a single ordinal preference in both rounds.

If the voters determine their preferences before the election and always vote directly consistent to them, they will emulate the contingent vote and get the same results as if they were to use that method. Therefore, in that model of voting behavior, the two-round system passes all criteria that the contingent vote passes, and fails all criteria the contingent vote fails.

Since the voters in the two-round system do not have to choose their second round votes while voting in the first round, they are able to adjust their votes as players in a game. More complex models consider voter behavior when the voters reach a game-theoretical equilibrium from which they have no incentive, as defined by their internal preferences, to further change their behavior. However, because these equilibria are complex, only partial results are known. With respect to the voters' internal preferences, the two-round system passes the majority criterion in this model, as a majority can always coordinate to elect their preferred candidate. Also, in the case of three candidates or less and a robust political equilibrium,[18] the two-round system will pick the Condorcet winner whenever there is one, which is not the case in the contingent vote model.

The equilibrium mentioned above is a perfect-information equilibrium and so only strictly holds in idealized conditions where every voter knows every other voter's preference. Thus it provides an upper bound on what can be achieved with rational (self-interested) coordination or knowledge of others' preferences. Since the voters almost surely will not have perfect information, it may not apply to real elections. In that matter, it is similar to the perfect competition model sometimes used in economics. To the extent that real elections approach this upper bound, large elections would do so less so than small ones, because it is less likely that a large electorate has information about all the other voters than that a small electorate has.

Tactical voting and strategic nomination

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Main articles: Strategic voting and Strategic nomination

Runoff voting is intended to reduce the potential for eliminating "wasted" votes by tactical voting. Under the plurality voting system (also known as first past the post), voters are encouraged to vote tactically, by voting for only one of the two leading candidates, because a vote for any other candidate will not affect the result. Under runoff voting, this tactic, known as "compromising", it is sometimes unnecessary because even if a voter's favorite candidate is eliminated in the first round, they will still have an opportunity to influence the result of the election by voting for a more popular candidate in the second round. However the tactic of compromising can still be used in runoff voting—it is sometimes necessary to compromise as a way of influencing which two candidates will survive to the second round. In order to do this it is necessary to vote for one of the three leading candidates in the first round, just as in an election held under the plurality method it is necessary to vote for one of the two leading candidates.

Runoff voting is also vulnerable to another tactic called "push over". This is a tactic by which voters vote tactically for an unpopular "push over" candidate in the first round as a way of helping their true favorite candidate win in the second round. The purpose of voting for the push over, in theory, is to ensure that it is this weak candidate, rather than a stronger rival, who survives to challenge one's preferred candidate in the second round. But in practice, such a tactic may prove counter-productive. If so many voters give their first preferences to the "weak" candidate that it ends up winning the first round, it is highly likely they will gain enough campaign momentum to have a strong chance of winning the runoff, too, and with it, the election. At the very least, their opponent would have to start taking the so-called weak candidate seriously, particularly if the runoff follows quickly after the first round.

Runoff voting can be influenced by strategic nomination; this is where candidates and political factions influence the result of an election by either nominating extra candidates or withdrawing a candidate who would otherwise have stood. Runoff voting is vulnerable to strategic nomination for the same reasons that it is open to the voting tactic of compromising. This is because a candidate who knows they are unlikely to win can ensure that another candidate they support makes it to the second round by withdrawing from the race before the first round occurs, or by never choosing to stand in the first place. By withdrawing candidates a political faction can avoid the spoiler effect, whereby a candidate "splits the vote" of its supporters. A famous example of this spoiler effect occurred in the 2002 French presidential election, when so many left-wing candidates stood in the first round that all of them were eliminated and two right-wing candidates advanced to the second round. Conversely, an important faction may have an interest in helping fund the campaign of smaller factions with a very different political agenda, so that these smaller parties end up weakening their own agenda.

The intention of runoff voting is that the winning candidate will have the support of an absolute majority of voters. Under the first past the post method 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 runoff voting is an artificial one. Instant-runoff voting and the exhaustive ballot are two other voting methods that create an absolute majority for one candidate by eliminating weaker candidates over multiple rounds. However, in cases where there are three or more strong candidates, runoff voting will sometimes produce an absolute majority for a different winner than the candidate elected by the other two.

Advocates of Condorcet methods argue[citation needed] 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 runoff voting the winning candidate is only matched, one-on-one, with one of the other candidates. When a Condorcet winner exists, the candidate does not necessarily win a runoff election due to insufficient support in the first round.

Runoff advocates counter[citation needed] that voters' first preference is more important than lower preferences because that is where voters are putting the most effort of decision and that, unlike Condorcet methods, runoffs 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.

Impact on factions and candidates

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Runoff voting encourages candidates to appeal to a broad cross-section of voters. This is because, in order to win an absolute majority in the second round, it is necessary for a candidate to win the support of voters whose favorite candidate has been eliminated. Under runoff voting, between rounds of voting, eliminated candidates, and the factions who previously supported them, often issue recommendations to their supporters as to whom to vote for in the second round of the contest. This means that eliminated candidates are still able to influence the result of the election. This influence leads to political bargaining between the two remaining candidates and the parties and candidates who have been eliminated, sometimes resulting in the two successful candidates making policy concessions to the less successful ones. Because it encourages conciliation and negotiation in these ways, runoff voting is advocated, in various forms, by some supporters of deliberative democracy.

Runoff voting is designed for single-seat constituencies. Therefore, like other single-seat methods, if used to elect a council or legislature it will not produce proportional representation (PR). This means that it is likely to lead to the representation of a small number of larger parties in an assembly, rather than a proliferation of small parties. In practice, runoff voting produces results very similar to those produced by the plurality method, and encourages a two-party system similar to those found in many countries that use plurality. Under a parliamentary system, it is more likely to produce single-party governments than are PR methods, which tend to produce coalition governments. While runoff voting is designed to ensure that each individual candidate elected is supported by a majority of those in their constituency, if used to elect an assembly it does not ensure this result on a national level. As in other non-PR methods, the party or coalition which wins a majority of seats will often not have the support of an absolute majority of voters across the nation.

Practical implications

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In smaller elections, such as those in assemblies or private organizations, it is sometimes possible to conduct both rounds in quick succession. More commonly, however, large-scale public elections the two rounds of runoff voting are held on separate days, and so involve voters going to the polls twice and governments conducting two elections. As a result, one of the most common criticisms against the two-round system is that the cost and difficulty of casting a ballot is effectively doubled.[19] However, the system may sometimes still be cheaper than holding a ranked-choice runoff (RCV), as the counting of votes in each round is simple. By contrast, ranked-choice runoff voting involves a longer and more complex count that often requires a centralized count, as it is impossible to tally or audit RCV results locally.[20][21]

The two-round voting system also has the potential to cause political instability between the two rounds of voting.[citation needed]

Usage

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The two-round system is the most common way used to elect heads of state (presidents) of countries worldwide, a total of 87 countries elect their heads of state directly with a two-round system as opposed to only 22 countries that used single-round plurality (first-past-the-post).[22]

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[23]

Legislative chambers exclusively elected by TRS in single-member districts

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Sub-national legislatures

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Legislatures elected by TRS in multi-member districts (block voting)

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  •   Iran – modified; 25% required to win in first round (unicameral)
  •   Kiribati (unicameral)
  •   Mongolia – modified; 28% required to win in first round (unicameral)
  •   Vietnam (unicameral)

Sub-national legislatures

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Legislatures partially elected by TRS (mixed systems)

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Other examples of use

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Two-round voting is used in French departmental elections. In Italy, it is used to elect mayors, but also to decide which party or coalition receives a majority bonus in city councils.[24]

Historically it was used to elect the Reichstag in the German Empire between 1871 and 1918 and the Storting of Norway from 1905 to 1919, in New Zealand in the 1908 and 1911 elections,[25][26] and in Israel to elect the Prime Minister in the 1996, 1999 and 2001 elections.[27]

Notes

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  1. ^ Some jurisdictions allow for runoffs with multiple candidates if the first round is tied, or if multiple candidates receive a sufficiently large number of votes.

References

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  1. ^ a b Sabsay, Daniel Alberto (1995). "El sistema de doble vuelta o ballotage" (PDF). Lecciones y Ensayos (62). Facultad de Derecho de la Universidad de Buenos Aires. ISSN 0024-0079. Archived (PDF) from the original on 2022-11-07. Retrieved 2024-07-18.
  2. ^ Martinelli, César (2002-10-01). "Simple plurality versus plurality runoff with privately informed voters". Social Choice and Welfare. 19 (4): 901–919. doi:10.1007/s003550200167. ISSN 1432-217X.
  3. ^ a b Aubin, Jean-Baptiste; Gannaz, Irène; Leoni-Aubin, Samuela; Rolland, Antoine (July 2024). A simulation-based study of proximity between voting rules.
  4. ^ "El ballotage, con raíces históricas en Francia". El Día. 1 November 2015. Archived from the original on 2023-10-23. Retrieved 2024-07-18.
  5. ^ a b Santucci, Jack; Shugart, Matthew; Latner, Michael S. (2023-10-16). "Toward a Different Kind of Party Government". Protect Democracy. Archived from the original on 2024-07-16. Retrieved 2024-07-16. Finally, we should not discount the role of primaries. When we look at the range of countries with first-past-the-post (FPTP) elections (given no primaries), none with an assembly larger than Jamaica's (63) has a strict two-party system. These countries include the United Kingdom and Canada (where multiparty competition is in fact nationwide). Whether the U.S. should be called 'FPTP' itself is dubious, and not only because some states (e.g. Georgia) hold runoffs or use the alternative vote (e.g. Maine). Rather, the U.S. has an unusual two-round system in which the first round winnows the field. This usually is at the intraparty level, although sometimes it is without regard to party (e.g. in Alaska and California).
  6. ^ Gallagher, Michael; Mitchell, Paul (2005-09-15). "The American Electoral System". The Politics of Electoral Systems. OUP Oxford. p. 192. ISBN 978-0-19-153151-4. American elections become a two-round run-off system with a delay of several months between the rounds.
  7. ^ Bowler, Shaun; Grofman, Bernard; Blais, André (2009), "The United States: A Case of Duvergerian Equilibrium", Duverger's Law of Plurality Voting: The Logic of Party Competition in Canada, India, the United Kingdom and the United States, New York, NY: Springer, pp. 135–146, doi:10.1007/978-0-387-09720-6_9, ISBN 978-0-387-09720-6, retrieved 2024-08-31, In effect, the primary system means that the USA has a two-round runoff system of elections.
  8. ^ Kousser, Thad. "California's jungle primary sets up polarized governor's race for November". The Conversation. Retrieved 2018-06-23. The idea was that by opening up primaries to all voters, regardless of party, a flood of new centrist voters would arrive. That would give moderate candidates a route to victory .. Candidates did not represent voters any better after the reforms, taking positions just as polarized as they did before the top two. We detected no shift toward the ideological middle.
  9. ^ Hill, Seth J.; Kousser, Thad (2015-10-17). "Turning Out Unlikely Voters? A Field Experiment in the Top-Two Primary". Political Behavior. 38 (2): 413–432. doi:10.1007/s11109-015-9319-3. ISSN 0190-9320. S2CID 54541384. Two groups that were predicted by advocates to increase their participation in response to this reform—those registered with third parties or no-party-preference registrants (independents) who were not guaranteed a vote in any party's primary before the move to the top-two—also show declines in turnout
  10. ^ McGhee, Eric; Masket, Seth; Shor, Boris; Rogers, Steven; McCarty, Nolan (April 2014). "A Primary Cause of Partisanship? Nomination Systems and Legislator Ideology". American Journal of Political Science. 58 (2): 337–351. doi:10.1111/ajps.12070. ISSN 0092-5853.
  11. ^ Patterson, Shawn (2020-12-01). "Estimating the unintended participation penalty under top-two primaries with a discontinuity design". Electoral Studies. 68: 102231. doi:10.1016/j.electstud.2020.102231. ISSN 0261-3794.
  12. ^ Merrill, Samuel (1984). "A Comparison of Efficiency of Multicandidate Electoral Systems". American Journal of Political Science. 28 (1): 23–48. doi:10.2307/2110786. ISSN 0092-5853. JSTOR 2110786. However, squeezed by surrounding opponents, a centrist candidate may receive few first-place votes and be eliminated under Hare.
  13. ^ Merrill, Samuel (1985). "A statistical model for Condorcet efficiency based on simulation under spatial model assumptions". Public Choice. 47 (2): 389–403. doi:10.1007/bf00127534. ISSN 0048-5829. the 'squeeze effect' that tends to reduce Condorcet efficiency if the relative dispersion (RD) of candidates is low. This effect is particularly strong for the plurality, runoff, and Hare systems, for which the garnering of first-place votes in a large field is essential to winning
  14. ^ a b Sabsay, Daniel Alberto (1995). "El sistema de doble vuelta o ballotage" (PDF). Lecciones y Ensayos (62). Facultad de Derecho de la Universidad de Buenos Aires. ISSN 0024-0079. Archived (PDF) from the original on 2022-11-07. Retrieved 2024-07-18.
  15. ^ "2024 French legislative elections: Results of the second round". France 24. 2024-07-04. Retrieved 2024-08-12.
  16. ^ "Proportional Representation Voting Systems of Australia's Parliaments". ECANZ. Archived from the original on 2023-03-02. Retrieved 2023-04-09.
  17. ^ Bhutanese National Assembly electoral system Archived 2018-10-17 at the Wayback Machine IPU
  18. ^ Messner; et al. (2002-11-01). "Robust Political Equilibria under Plurality and Runoff Rule" (PDF). Archived from the original (PDF) on 2010-06-12. Retrieved 2011-06-04.
  19. ^ "RCV versus Two-Round Runoff". FairVote. Retrieved 17 March 2022.
  20. ^ "Approval Voting vs. RCV". The Center for Election Science. Retrieved 17 March 2022.
  21. ^ Macaraeg, Sarah. "Instant runoff voting: What Shelby County data and real-world examples show". Commercial Appeal. Archived from the original on 21 May 2022. Retrieved 17 March 2022.
  22. ^ "IDEA Electoral system database". Retrieved 2024-09-30.
  23. ^ "Togo changes law to let president stand for two more terms". Archived from the original on 2020-01-31. Retrieved 2020-06-30.
  24. ^ The usefulness of the link between different political forces in the second ballot is (...) a convergence of interests: Buonomo, Giampiero (2000). "Al candidato sindaco non eletto spetta sempre almeno un seggio". Diritto&Giustizia Edizione Online. Archived from the original on 2016-03-24. Retrieved 2016-03-20.
  25. ^ Fiva, Jon H.; Hix, Simon (2020). "Electoral Reform and Strategic Coordination". British Journal of Political Science. 51 (4): 1–10. doi:10.1017/S0007123419000747. hdl:11250/2983501. ISSN 0007-1234.
  26. ^ Fiva, Jon H.; Smith, Daniel M. (2017-11-02). "Norwegian parliamentary elections, 1906–2013: representation and turnout across four electoral systems". West European Politics. 40 (6): 1373–1391. doi:10.1080/01402382.2017.1298016. hdl:11250/2588036. ISSN 0140-2382. S2CID 157213679.
  27. ^ "Basic Law – The Government (1992)". Knesset of Israel. Archived from the original on 2020-08-12. Retrieved 2020-07-24.
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