Majority Runoff

Consider France, 2002. In the first round of the presidential election, the vote splintered across sixteen candidates, and the far-right's Jean-Marie Le Pen edged out the sitting Socialist prime minister to reach the runoff. Two weeks later, voters who despised Le Pen — left, right, and center — poured in behind Jacques Chirac, who won the second round with 82% of the vote. That is majority runoff doing exactly what it is designed to do: forcing a final choice between two candidates so the winner leaves with a genuine majority behind them, even a majority assembled out of opposition.

The rule is mechanically simple. Round one: a candidate with more than 50% of valid votes wins outright. If none does, a second round — typically two to four weeks later — pits the top two finishers against each other, and one of them necessarily crosses 50%. The system, known variously as the two-round system (TRS) or ballotage, elects presidents in France (under the Fifth Republic since 1965), Brazil, Argentina, Poland, Portugal, Austria, Finland, Turkey, and Indonesia, among many others; France also uses a variant for National Assembly seats with different second-round qualification rules.

Contrast it against its two main rivals to see what it buys and costs. Against plurality (first-past-the-post), runoff frees voters to cast a sincere first-round vote for their true favorite and a strategic second-round vote for the lesser evil, and it pressures parties to build broad coalitions between rounds. Maurice Duverger argued that runoff systems therefore tend toward multipartism with bipolar coalitions, where plurality tends toward two parties (Duverger's law). Against instant-runoff voting (IRV), the difference is machinery: IRV simulates the runoff inside a single ranked ballot, eliminating last-place candidates and transferring votes in one count, whereas majority runoff requires voters to physically return for a separate election day.

The costs are real and recurring. Two elections cost more to run, and turnout often sags in the second round — voter fatigue. Social-choice theorists point to a subtler flaw: the Condorcet winner — the candidate who would beat every rival head-to-head — can be eliminated in round one if their first-preference support is thinly spread, so the 'majority' the runoff produces may not be the most broadly acceptable outcome. And leaders don't always survive: 'runoff reversals,' where the first-round leader loses the second round as third-place voters consolidate behind the runner-up, happen regularly — Chile 1999, Peru 2006, Guatemala 2023.

Many countries also file down the pure model to avoid runoffs when a front-runner is clearly dominant. Argentina lets a candidate win in round one with 45% of the vote, or with 40% and a ten-point lead over the runner-up (1994 Constitution, Arts. 97–98). Costa Rica sets the first-round bar at 40%; Ecuador and Nicaragua use similar reduced thresholds, sometimes classed as qualified plurality rather than strict majority runoff. The trade-off is explicit: lower the threshold and you save the cost and fatigue of a second round, at the price of a winner with weaker majority backing.