St. Charles County, Missouri

Missouri House District 105

2 candidates are tracked for Missouri House District 105 on the November 3, 2026 ballot: Colin Wellenkamp and Cat Clayton. Candidate information follows official St. Charles County election filings; verify with the official election office linked below.

About this race

Colin Wellenkamp (Republican), Cat Clayton (Democratic) meet on the November 3 ballot; Colin Wellenkamp is the sitting member per the House roster. Missouri has no runoffs; the August 4 primary winner of each party is the nominee, and unopposed nominees still print. The field is the Missouri Secretary of State's certified general election candidate list (certified August 25, 2026). This seat is elected by district; only the district covering your address appears on your ballot.

What this office does

State legislator. State legislators write and vote on state laws and the state budget, which fund schools, roads, prisons, universities and health programs, and set the rules for local governments and elections. Each member represents one district and serves on committees that shape bills before a floor vote. Terms are two years in most state houses and four in most state senates.

This race. Elected by district: only voters who live in the district see this race on their ballot. The sitting officeholder, Colin Wellenkamp, is on the ballot.

Missouri › St. Charles County › Missouri House District 105

Colin Wellenkamp

Republican Incumbent

Top priorities

Supporting law enforcement agencies
Securing resources for St. Charles County schools
Improving water and transportation infrastructure

Per the campaign site.

Biography

Colin Wellenkamp has more than two decades of experience in sustainable development and environmental policy, per the campaign site. He founded and leads the Mississippi River Cities and Towns Initiative, coordinating 102 mayors across ten states, and has taught sustainability and economics at Washington University and Saint Louis University, per the campaign site.

Campaign site (opens in a new tab)

Cat Clayton

Democratic

Top priorities

Lowering costs for families
Strengthening public schools
Protecting access to healthcare

Per the candidate questionnaire.

Biography

Cat Clayton is a software and data engineer and community advocate, per her candidate profile with the recruitment group Leaders We Deserve. Her father and husband have both served in the military. No campaign website was found as of September 6, 2026.

Next on your ballotMissouri House District 106

See your full ballot

Voting info and more

Questions about this race

Who is running for Missouri House District 105 in 2026?

When is the Missouri House District 105 election in Missouri?

Election Day is Tuesday, November 3, 2026. Registration deadlines, early voting dates and mail ballot rules for Missouri are on the Missouri election hub at theballotbrief.com.

How do I see my exact St. Charles County ballot?

Enter your ZIP code in the lookup at theballotbrief.com for the statewide and congressional races, or a full street address to add the county, city and district contests for that location.

Verify this race

Candidate roster from official St. Charles County and state election office filings, last verified October 2, 2026. Bios and priorities carry their attribution inline.

Cross-check with the official Missouri election office, or see the full St. Charles County sample ballot and your exact ballot by address.

The rest of your St. Charles County ballot

25 tracked races in St. Charles County, Missouri. Landed here from another county's search? Look up your own ballot below.

Also on your ballot

Missouri House District 107 Missouri House District 108 Missouri Senate District 2 See all 25 St. Charles County races

Candidate profiles

Colin Wellenkamp, full profile Cat Clayton, full profile Official Missouri election office