Oklahoma Gov. Kevin Stitt is considering five candidates to replace Sen. Markwayne Mullin (R-OK), who President Trump tapped to become the next Secretary of Homeland Security.
Stitt must appoint a replacement within 30 days after Mullin formally vacates his seat.
News9 shared the list of candidates:
- Nathan Dahm — Served as chair of the Oklahoma Republican Party from 2023 to 2025. Previously served as an Oklahoma state senator from 2012 to 2024.
- David Ostrowe — Currently serves as chief operating officer in the governor’s office.
- John O’Connor — Served as Oklahoma attorney general from 2021 to 2023.
- Dustin Hilliary — Currently serves as a senior advisor to Stitt. Hilliary is co-CEO of Hilliary Communications.
- Harold Hamm — An oil and gas executive and billionaire best known as the founder of Continental Resources and a noteworthy figure in the U.S. shale oil boom.
A second source familiar with the situation tells News 9 that Hilliary was contacted by the governor’s office regarding the Senate appointment.
🚨Report: Oklahoma Governor Kevin Stitt is reviewing five possible replacements for Sen. Markwayne Mullin
The 5 Candidates
Nathan Dahm: Former Oklahoma Republican Party chair and State Senator
John O’Connor: Former Oklahoma Attorney General
Dustin Hilliary: Senior advisor to… pic.twitter.com/wccZWB2tuc
— The Calvin Coolidge Project (@TheCalvinCooli1) March 8, 2026
Mullin is scheduled to begin serving as Homeland Security secretary on March 31st.
The appointment would remain in effect until Oklahoma's next statewide election.
According to The Hill, the appointee "must pledge not to run for a full term afterward."
The Republican senator said he was "super excited" for the opportunity.
Take a listen:
"I am super excited about this opportunity."
Sen. Markwayne Mullin spoke with reporters after President Trump announced Mullin will replace Kristi Noem as Department of Homeland Security secretary. https://t.co/xJvu7mZTV4 pic.twitter.com/EIcQyDVsBy
— ABC News (@ABC) March 5, 2026
More from The Hill:
Speculation about the race quickly grew after news of Mullin’s selection to Trump’s Cabinet, with several top Oklahoma figures rising to the top of the potential list.
“‘Who is considering running?’ The prevailing view in Oklahoma … is that ‘Who is not considering?’ — that might be a shorter list,” said Bob Burke, a constitutional expert and attorney in the state.
Two Republicans were quick to throw their names into the mix of potential candidates.
Rep. Kevin Hern (R-Okla.), a wealthy businessman who could help self-finance a potential campaign, told reporters at the Capitol on Thursday, “Stay tuned for the announcement next week.”
Tyler Powell, a partner at Oklahoma-based political strategy firm CSS Partners, told The Hill that, “based on some intel we’ve got, he [Hern] is going to announce next week.” Powell said he expects to “wake up on Monday or Tuesday and see a Hern announcement.”
Rep. Stephanie Bice (R-Okla.) — who proved she could win a competitive race by unseating former Rep. Kendra Horn (D) in 2020 — also teased a potential run.
ADVERTISEMENT“It’s the honor of a lifetime to stand side by side with President Trump for the people of Oklahoma,” Bice wrote Thursday on the social platform X. “I’ve received encouragement from every corner of this great state to run for the US Senate. And it’s something I’m carefully considering.”
“Stay tuned!” she added.
Oklahoma Republican strategist Pat McFerron, founding partner of CMA Strategies, said he thinks the race is Hern’s to lose.
