How Runoff Primaries Work

How the Primary Process in 10 States Could Help Solve Hyper-Partisanship

Primary Voting
Voters in 11 states take part in runoff primaries, according to the National Conference of State Legislatures. Rick Friedman / Corbis via Getty Images

Runoff primaries are held in nearly a dozen states when no candidate in a race for their party's nomination for state or federal office is able to win a simple majority of the vote. Runoff primaries amount to a second round of voting, but only the two top vote-getters appear on the ballot - a move that ensures one of them will win support from at least 50 percent of voters. All other states require the nominee to win only a plurality, or the most number of votes in the race. 

"This requirement that you have a majority vote is hardly unique. We require the president to get a majority in the Electoral College. Parties have to get majorities to choose presidents. As John Boehner can explain, you also need to have majority support in the House to become speaker," Charles S. Bullock III, a political scientist at the University of Georgia, said during a 2017 panel discussion held by the National Conference of State Legislatures.

Runoff primaries are most common in the South and date back to single-party rule. The use of runoff primaries is more likely when there are more than two candidates seeking the nomination for a statewide seat such as governor or U.S. senator. The requirement that party nominees win at least 50 percent of the vote is seen as a deterrent to electing extremist candidates, but critics argue holding second primaries to achieve this goal is costly and often alienates large swaths of potential voters. 

10 States That Use Runoff Primaries

The states that require nominees for state and federal office to win a certain threshold of votes and hold runoff primaries when that doesn't happen, according to FairVote and the National Conference of State Legislatures, are:

  • Alabama: Requires nominees to win at least 50 percent of the vote. 
  • Arkansas: Requires nominees to win at least 50 percent of the vote. 
  • Georgia: Requires nominees to win at least 50 percent of the vote. 
  • Louisiana: Requires nominees to win at least 50 percent of the vote. 
  • Mississippi: Requires nominees to win at least 50 percent of the vote. 
  • North Carolina: Requires nominees to win at least 40 percent of the vote. 
  • Oklahoma: Requires nominees to win at least 50 percent of the vote. 
  • South Carolina: Requires nominees to win at least 50 percent of the vote. 
  • South Dakota: Requires certain nominees to win at least 35 percent of the vote. 
  • Texas: Requires nominees to win at least 50 percent of the vote. 

History of Runoff Primaries

The use of runoff primaries dates to the South in the early 1900s, when Democrats held a lock on electoral politics. With little competition from Republican or third parties, the Democrats essentially chose their candidates not in the general election but the primaries; whoever won the nomination was guaranteed electoral victory.

Many southern states set artificial thresholds to protect white Democratic candidates from being toppled by other candidates who won with mere pluralities. Others such as Arkansas authorized the use of runoff elections to block extremists and hate groups including the Ku Klux Klan from winning party primaries.

Justification for Runoff Primaries

Runoff primaries are used for the same reasons today: they force candidates to achieve support from a broader portion of the electorate, thereby reducing the chance voters will elect extremists.

According to Wendy Underhill, an expert on elections and redistricting, and researcher Katharina Owens Hubler:

"The requirement for a majority vote (and thus the potential for a primary runoff) was intended to encourage candidates to broaden their appeal to a wider range of voters, to reduce the likelihood of electing candidates who are at the ideological extremes of a party, and to produce a nominee who may be more electable in the general election. Now that the South is solidly Republican, the same issues still hold true."

Some states have also moved to open primaries to try to reduce partisanship.

Downsides of Runoff Primaries

Turnout data show that participation declines in runoff elections, meaning those who do turnout might not fully represent the interests of the district as a whole. And, of course, it costs money to hold primaries. So taxpayers in states that hold runoffs are on the hook for not one but two primaries.

Instant Runoff Primaries

An alternative to runoff primaries growing in popularity is the "instant runoff." Instant runoffs require the use of "ranked-choice voting" in which voters identify their first, second and third preferences. The initial count uses every voter's top choice. If no candidate hits the 50-percent threshold to secure the party nomination, the candidate with the fewest votes is dropped and a recount is held. This process is repeated until one of the remaining candidates gets a majority of votes. Maine became the first state to adopt ranked-choice voting in 2016; it uses the method in state races including those for​ the legislature. 

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Murse, Tom. "How Runoff Primaries Work." ThoughtCo, Feb. 16, 2021, Murse, Tom. (2021, February 16). How Runoff Primaries Work. Retrieved from Murse, Tom. "How Runoff Primaries Work." ThoughtCo. (accessed March 5, 2021).