Highest rate of Missouri state senators facing primary challengers since 2014

Six of the nine Missouri state senators running for re-election—all Republicans—face contested primaries. That equals 67% of incumbents seeking re-election, the highest rate since 2014. This is also the first cycle since 2014 with more than one Republican incumbent facing primary challengers.

A primary is contested when there are more candidates running than available nominations, meaning at least one candidate must lose. Historically, however, Missouri incumbents tend to win contested primaries.

Since 2014, only one state senator—Sen. Jacob Hummel (D)—has lost to a primary challenger in Missouri. This means that during that time, 86% of incumbents in contested primaries ultimately advanced to the general election.

The total number of contested primaries—including those without incumbents—is also at its highest point this year. With 17 districts holding elections, there are 34 possible primaries every election cycle.

This year, there are 13 contested primaries, all among Republicans. This is the first time since 2014 without any contested Democratic primaries in the chamber. All but four districts up for election will have a contested Republican primary.

The filing deadline for candidates running for state Senate in Missouri was March 29. Candidates filed to run for 17 of the state’s 34 Senate districts.

Overall, 51 major party candidates filed to run in the chamber this year: 12 Democrats and 39 Republicans.

Missouri has been a Republican trifecta since the party won the governorship in 2016. Republicans currently hold a 24-10 majority in the Senate and a 108-48 majority in the House.

Missouri’s primaries are scheduled for August 2, the tenth statewide primary date of the 2022 state legislative election cycle.

Ninety-two percent of state legislative incumbents filed for re-election in 2021

In 2021, state legislative incumbents filed for re-election at a higher rate than any other year in the past decade other than 2013. When an incumbent does not run for re-election, his or her seat is left open, meaning it is guaranteed to a newcomer at the start of the next state legislative session.

Of the 220 seats up for election this year, 92.3% of incumbents (203) filed for re-election, leaving 7.7% of seats (17) open. From 2011 to 2021, only the state legislative elections held in 2013 saw a lower percentage of open seats at 6.8%.

Two states—New Jersey and Virginia—are holding state legislative elections in 2021. These states hold elections every two years in odd-numbered years.

In New Jersey, 120 seats are up for election, 10.0% of which (12) are open. Of those open seats, six were most recently held by Democrats and six by Republicans.

Compared to previous elections, New Jersey’s rate of open seats in 2021 is tied with 2017 for the state’s second-highest percentage of open seats in the past decade.

In Virginia, 100 seats are up for election, 5.0% of which (5) are open, a decade-low rate for the state. Of those five open seats, one was most recently held by a Democrat and four by Republicans.

Neither New Jersey nor Virginia has state legislative term limits, meaning all open seats this year were left by incumbents voluntarily choosing not to file for re-election. Of the four states that hold state legislative elections in odd-numbered years, only one—Louisiana—has term limits. 

As shown by the chart below, term limits can have a varying effect on the total number of open seats. In 2011, 15.2% of open seats were caused by term limits, while in 2019, term limits accounted for 45.6% of all open seats.

In the chart below, a voluntary open seat is one where an incumbent chose not to file for re-election. A term-limited open seat is one where an incumbent could not seek re-election due to term limits.

This analysis was conducted as part of Ballotpedia’s annual state legislative competitiveness study. In addition to open seats, this study includes an analysis of incumbents in contested primaries and seats with major party competition in the general election. 

To learn more about open seats in the 2021 state legislative elections, click here.