The majority vote rule and runoff primaries in the United States

The major parties in the United States use primary elections to select party candidates for general elections. While most employ a simple plurality vote rule for this purpose, some states, primarily southern, employ a majority rule that requires a runoff between the top two vote recipients if no candidate receives a majority in the initial primary. Data on primaries for state Governor and U.S. Senator from 1980 to 2002 are used to examine contemporary concerns about runoffs. Included in the findings are (1) the problem that majority runoffs address – candidates being selected based on low levels of voter support is not a frequent outcome under the plurality rule; (2) the vast majority of selections is based on a majority of votes in a primary, regardless of whether a simple plurality or majority is required; and (3) runoff primaries are necessary in roughly one-third of the contested primaries held in the majority vote context, and in about one-third of them the primary leader loses the runoff.