In ten states, a primary runoff election may be held if no candidate wins a majority of the votes cast in their party’s primary. States currently using primary runoffs include Alabama, Arkansas, Georgia, Louisiana, Mississippi, North Carolina (30% threshold), Oklahoma, South Carolina, South Dakota (35% threshold), and Texas. FairVote studied voter turnout in all congressional primary runoffs held since 1994. Below are our key findings.
Near-Universal Decline in Turnout. Turnout declined between the primary and the runoff in 240 of the 248 regularly scheduled primary runoffs in the U.S House and U.S. Senate from 1994 to 2020. In other words, in 97% of primary runoff elections fewer people voted in the second round than in the first. The average decline in turnout was 38% and the median decline was 37%.
Primary-Runoff Timing a Key Factor. The longer the wait between the initial primary and the runoff, the higher the decrease in voter turnout between elections. Runoffs held between 31 and 40 days after the initial primary have a median turnout decline over three times higher than that of runoffs held between 11 and 20 days after the initial primary.
Runoffs Nominate Winning Candidates for the General Election. Of the 248 runoffs in this time period, 79 (32%) resulted in a primary winner who trailed in the first round. Forty-one of these went on to win the general election. These congresspeople had the broadest support in their districts, but would not have been elected to Congress under plurality voting. Despite their faults regarding voter turnout decline, runoffs aim to achieve an important goal: avoiding unrepresentative winners who do not have majority support.
A spreadsheet with the raw data can be found here.