Markwayne Mullin resigned from the Senate in March 2026 after being confirmed as Secretary of Homeland Security. Gov. Stitt appointed Alan Armstrong (Williams Companies exec) as caretaker — who agreed not to seek a full term. The 2026 election is now an open Republican primary. James Lankford (R, Class 3) was re-elected in 2022 and is NOT up until 2028.
- Open seat — Mullin resigned (confirmed DHS Secretary, March 2026). Caretaker Alan Armstrong agreed not to run. The November 2026 winner serves a full six-year Class 2 term.
- Kevin Hern (Rep. OK-01) is the Republican frontrunner: Trump-endorsed (March 13, 2026), $8.2M raised, launched campaign March 11. Republican primary June 16, 2026 — runoff August 25 if no one reaches 50%.
- Race rated Safe Republican — Trump won Oklahoma by 34.3 points in 2024 (66.2%–31.9%). Democrats have not won an Oklahoma Senate race since David Boren in 1990.
- James Lankford (R, Class 3) — re-elected 2022, next election 2028 — is NOT on the 2026 ballot.
Key Facts — Oklahoma Senate 2026
Republican Primary Candidates
Kevin Hern — Republican Frontrunner
Kevin Hern has served as U.S. Representative for Oklahoma’s 1st Congressional District (Tulsa area) since 2019. A McDonald’s franchise owner and businessman before entering politics, Hern positioned himself as a Trump loyalist and fiscal conservative throughout his House tenure. He announced his Senate campaign on March 11, 2026 — just days after Mullin’s DHS confirmation became imminent — and secured President Trump’s endorsement within 48 hours (March 13, 2026). Trump’s endorsement effectively cleared the field of high-profile competition.
By the end of March 2026, Hern had raised $8.2 million for the Senate race — a substantial financial advantage over the other Republican primary candidates. With Trump’s backing, endorsements from multiple Republican senators, and a fundraising edge, Hern entered the June 16 Republican primary as the overwhelming favorite. If he wins the primary (or the August 25 runoff), he is expected to win the November 3 general election by a wide margin in a state that has not elected a Democratic senator in over 30 years.
How the Seat Became Open — Mullin to DHS Secretary
Markwayne Mullin had won the November 2022 special election for the Class 2 seat vacated by Jim Inhofe, defeating Democrat Kendra Horn by 14.6 points. He served as a senator since January 2023 while retaining his profile as one of the Senate’s more combative members — best known nationally for challenging Teamsters president Sean O’Brien to a physical confrontation during a 2023 Senate hearing.
In early 2026, President Trump nominated Mullin to replace Kristi Noem as Secretary of Homeland Security. Mullin’s Senate confirmation hearing was held March 18, 2026. Following confirmation, he resigned his Senate seat — creating the Class 2 vacancy. Oklahoma Governor Kevin Stitt moved quickly, appointing Williams Companies Executive Chairman Alan Armstrong on March 24, 2026. Armstrong, who had no prior elected experience, agreed as a condition of appointment not to seek a full term in November 2026, making his role purely transitional.
Historical Results — Oklahoma Senate (Class 2)
Jim Inhofe held this Class 2 seat from 1994 to January 2023 — nearly three decades. Mullin’s 2022 special election win (R +14.6) was closer than most Oklahoma Senate races due to Kendra Horn’s profile as a former congresswoman. The last Democrat to win the seat was David Boren (re-elected 1990, resigned 1994 to become OU president).
2026 Senate Race Context & National Outlook
The 2026 midterm elections are taking place in an environment shaped by significant economic uncertainty. Trump's Liberation Day tariffs triggered a consumer confidence collapse and PCE inflation surged to 4.5% in Q1 2026. The Trump approval rating stands at 38.1% approve / 59.2% disapprove — among the lowest for any first-year president since modern polling began. The Generic Ballot shows Democrats with a consistent +6.0 advantage, a historically predictive indicator of significant House seat gains.
In the Senate, 33 Class 2 seats are up in 2026. Republicans must defend seats in Georgia, Iowa, North Carolina, Alaska, and Texas, while Democrats defend Nevada, New Hampshire, Michigan, Minnesota, and Virginia. Key battleground races that will determine Senate control include Georgia (Jon Ossoff, D), Iowa (open seat, Ernst retires), Nevada (Jacky Rosen, D), and Alaska (Lisa Murkowski, R). The full Senate map is at the Senate 2026 overview.
Issue-level polling context: The top issues driving 2026 are the economy and tariffs, healthcare, immigration, and Social Security. See the Battleground Tracker for the latest state-level polling and the Trump Policy Tracker for executive action context.
Frequently Asked Questions
Who is running for Senate in Oklahoma in 2026?
The 2026 Oklahoma Senate race is an open seat after Mullin resigned to become DHS Secretary. Kevin Hern (Rep. OK-01, Tulsa) is the Republican frontrunner with Trump's endorsement and $8.2 million raised. Republican primary: June 16, 2026. Democrats have fielded candidates but Oklahoma is rated Safe Republican.
Why did Markwayne Mullin leave the Senate?
President Trump nominated Mullin as Secretary of Homeland Security to replace Kristi Noem. He was confirmed and resigned his Senate seat in March 2026. Governor Stitt appointed Alan Armstrong as caretaker senator, who agreed not to seek the full six-year term in the November 2026 election.
Is James Lankford up for re-election in 2026?
No. James Lankford (R, Class 3) was re-elected in November 2022 by 34 points and serves until January 2029. The 2026 Oklahoma race is for the Class 2 seat — formerly Inhofe's, then Mullin's, now held by caretaker Armstrong.
When did Democrats last win an Oklahoma Senate race?
The last Democrat to win an Oklahoma Senate race was David Boren in 1990. Boren resigned in 1994 to become president of the University of Oklahoma. Republicans have held both Oklahoma Senate seats by large margins ever since.