Two-round system

The two-round system (TRS or 2RS), sometimes called ballotage, top-two runoff, or two-round plurality, is a single-winner electoral system which aims to elect a member who has support of the majority of voters. The two-round system involves two rounds of choose-one voting, where the voter marks a single favorite candidate in each round. The two candidates with the most votes in the first round move on to a second election (a second round of voting). The two-round system is in the family of plurality voting systems that also includes single-round plurality (FPP). Like instant-runoff (ranked-choice) voting and first past the post, it elects one winner.

The two-round system first emerged in France and has since become the most common single-winner electoral system worldwide. Despite this, runoff-based rules like the two-round system and RCV have faced criticism from social choice theorists as a result of their susceptibility to center squeeze (a kind of spoiler effect favoring extremists) and the no-show paradox. This has led to the rise of electoral reform movements which seek to replace the two-round system with other systems like rated voting, particularly in France.

As well, TRS means voters sometimes have to gather to vote a second time, and sometimes the intervening period of time is rife with discord.

In the United States, the first round is often called a jungle or top-two primary. Georgia, Louisiana, California, and Washington use the two-round system for all non-presidential elections. Mississippi uses it for state offices. Most other states use a partisan primary system that is often described as behaving like a two-round system in practice, with primaries narrowing down the field to two frontrunners. (Alaska and Maine use the Instant-runoff voting system, a single-winner ranked-choice voting (RCV) system, which, unlike TRS, does not require voters to engage in multiple rounds of voting.)

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". The rule has since gained substantial popularity in South America, Eastern Europe, and Africa, where it is now the dominant system.

Some variants of the two-round system use slightly different rules for eliminating candidates before the second round, allowing more than two candidates to proceed to the second round in some cases. Under such systems, in the second round it is sufficient for a candidate to receive a plurality of votes (more votes than anyone else), not necessarily a majority, to be elected.

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: