Two-round system

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The two-round system (TRS or 2RS) is a voting method used to elect a single winner. In the United States, it is often called a jungle or nonpartisan primary. The system can also be called runoff voting, though this term is sometimes used to refer to the closely-related exhaustive ballot and ranked-choice (instant-runoff), which tend to produce highly similar results.

In a two-round system, both rounds are held using choose-one voting, where the voter marks their favorite candidate. The two candidates with the most votes in the first round proceed to a second round, where all other candidates are excluded.^{[note 1]} The two-round system is widely used in the election of legislative bodies and directly elected presidents. It is closely related to other members of the plurality-runoff family of methods (including plurality voting, ranked-choice voting, and plurality-with-primaries).

The two-round system first emerged in France, and has since become the most common single-winner electoral system worldwide.^[1][2]

In the United States the system is used to elect most public officials in Mississippi, Georgia, Louisiana, and along the West Coast. For most of the rest of the country, and for Presidential elections, a partisan primary system is used.^[3]

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