Four hundred twenty-two candidates, the second most in any year since 2010, are running in Missouri’s Aug. 4 primaries. All 163 seats in the Missouri House of Representatives and 17 seats in the Missouri Senate are up for election this year.

There are 62 open seats with no incumbent running for re-election. This is the third most in any year since 2010.

There are 23 Democratic primaries and 46 Republican primaries, for a total of 69 (19.2%). There were an average of 24 Democratic primaries and 46 Republican primaries in election cycles between 2010 and 2024.

There are 118 incumbents running for re-election, 22 of whom are contested. An average of 127 incumbents ran in cycles between 2010 and 2024 and an average of 24 of those incumbents were contested each year. 

Missouri is one of eight states in which fewer than 5% of seats would need to change party control to break an existing supermajority. Ballotpedia calls those state supermajorities highly exposed to breaking. Of these states, five have Republican supermajorities, and three have Democratic supermajorities. Click here to learn more about our supermajority analysis.

Republicans hold a 106-52 majority in the Missouri House, with five vacancies, and a 23-10 supermajority with one vacancy in the state Senate. In Missouri, a two-thirds vote is required in both chambers to override the governor’s vetoes. When there are no vacancies, this amounts to 23 votes in the Senate and 109 votes in the House. 

Republicans have had majorities in both chambers of the Legislature since 2003 and a trifecta in Missouri since 2017. The last time Democrats controlled either chamber was in 2002, when they last had a majority in the House. The last time Democrats had a trifecta in Missouri was 2000.

Click here to learn more about Missouri's 2026 state Senate elections and here to learn more about Missouri's 2026 state House elections.