Markwayne Mullin: Everything to Know About Trump’s Homeland Security Secretary Pick

If you follow Oklahoma politics, your phone probably blew up yesterday. Around noon on March 5, President Trump dropped a Truth Social post that sent shockwaves through the Sooner State: Kristi Noem was out at DHS, and Markwayne Mullin was in .

I spent the last 24 hours on the phone with sources and digging through the fine print of state law. The result is this guide. It cuts through the speculation and tells you exactly what happens now, who is actually running, and—most importantly—who will replace Markwayne Mullin in the U.S. Senate.

The News That Broke Yesterday: Noem Out, Mullin In

Let‘s get the facts straight first. This wasn’t a slow leak. It was a thunderclap.

On Thursday, March 5, Trump announced on Truth Social that Senator Markwayne Mullin (R-OK) would become the new Secretary of Homeland Security. The effective date is March 31, 2025.

Why did Noem leave? Reports suggest the White House was unhappy with her testimony regarding a $200 million ad campaign that featured herself.

There was also controversy over her referring to two U.S. citizens killed by federal agents as "domestic terrorists". Trump gave her a soft landing, however, moving her to a new role as Special Envoy for "The Shield of the Americas"—a Western Hemisphere security initiative launching this Saturday in Doral, Florida.

For Oklahoma, the headline is simple: We have a Senate vacancy.

Breaking Down the Replacement Rules (It‘s Weird)

I’ve covered a few of these vacancies. This one is different. Back in 2021, the state legislature got tired of expensive special elections. They passed a law that creates a two-step process. Here is how it works for Mullin‘s seat:

Step 1: The Governor's Pick (The "Placeholder")

Governor Kevin Stitt gets to appoint someone immediately after Mullin resigns. This person will be a senator by April. However, they are legally barred from running in the special election.

Think of them as a seat-warmer. They keep the office staffed, vote on legislation, but cannot campaign for the job permanently.

Step 2: The November Election (The Real Race)

Because Mullin was elected in 2022 to finish Jim Inhofe‘s term, this is technically a special election to finish that term. It will happen on November 3, 2025.

Critical Dates to Watch:

March 31, 2025: Mullin resigns to join DHS.
April 1-3, 2025: Candidate filing period opens for the federal seat.
Late April 2025: Governor Stitt announces his appointee (likely after the filing deadline to avoid influencing it).

Who Will Replace Markwayne Mullin? The Real Candidates

Forget the placeholder. You want to know who is actually going to be your senator in 2027. Based on reporting from The Hill and the Washington Examiner over the last 24 hours, here is the breakdown of who is in and who is likely in.

The Confirmed Contenders

Kevin Hern (R-OK-01)

Hern is the heavy hitter. He represents Tulsa, chairs the House Republican Policy Committee, and sits on the powerful Ways and Means Committee.

His Move: He confirmed to reporters on Thursday that he is considering a run. He told them, "Stay tuned for the announcement next week".
His Money: This matters. Hern is a former McDonald's franchise owner who made millions. Reports indicate he is willing to loan his campaign $5 million on top of the $2.4 million he already has in the bank. In a fast primary, money buys name ID instantly.

Stephanie Bice (R-OK-05)

Bice represents Oklahoma City and has proven she can win tough races. She beat Kendra Horn in 2020.

Her Move: A source familiar with her thinking confirmed she is considering a run. She is not interested in the interim appointment because she wants to keep her House seat until the election.
Her Position: She sits on the House Appropriations Committee. She is viewed as a bridge between the mainstream conservatives and the establishment.

The Wildcard

T.W. Shannon
You remember him. He is the former Speaker of the Oklahoma House who lost to Mullin in a nasty runoff in 2022.

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The Chatter: His name is being floated heavily by national conservative groups. He would energize the base instantly. However, he hasn't held office in years, and he has to answer for that 2022 loss.

The Governor's Shortlist (For the Placeholder Role)

Governor Stitt needs an appointee. Since that person cannot run in November, he needs someone loyal who won't cause drama. NOTUS and the Washington Examiner report the shortlist includes:

Lt. Gov. Matt Pinnell: A popular figure who might be positioning for a future run.
Donelle Harder: A longtime adviser to Stitt.
Former Attorney General John O'Connor.

My Take: How This Race Plays Out

I‘ve watched these candidates for years. Here is the reality check.

Hern has the edge—right now. He has the money, the seniority, and he’s been quietly running for this his entire career. When Senator James Lankford was asked about Hern, he called him "very sharp. That‘s the establishment signal.

Bice is the underdog with a path. If she runs, she splits the Oklahoma City vote with Hern (who also has Tulsa money). It becomes a regional war. But Bice needs to convince donors she can win a statewide primary, which is much more conservative than her district.

Shannon is the X-Factor. If Shannon jumps in, he consolidates the anti-establishment vote. He forces Hern and Bice to fight over the center, while he runs to the right. That runoff in 2022 proved he can get 45% of the vote against a popular incumbent.

What Mullin Faces at DHS

While we focus on the Senate race, Mullin has a real job to do. He takes over an agency with 240,000 employees. He oversees TSA at airports, the Secret Service, FEMA during disasters, and Border Patrol.

Trump called him a "MAGA Warrior" and praised his background as an undefeated MMA fighter. But running DHS is less about fighting and more about managing.

Interestingly, Mullin brings a unique perspective. As the only Native American in the Senate, he has credibility on tribal issues—a major factor because DHS handles law enforcement on tribal lands and near the Northern Border.

He already has at least one Democratic supporter. Senator John Fetterman (D-PA) posted on X: "I‘m not sure how many fellow Democrats will vote to support our colleague @SenMullin as the next DHS Secretary, but I am AYE". That suggests his confirmation should be smooth.

When is Markwayne Mullin Up for Reelection?

This question is causing confusion. Let me clarify.

Markwayne Mullin is not up for reelection. He is resigning. The person elected in November 2025 will serve the remainder of his term.

However, because Mullin was originally elected to finish Inhofe's term, the "remainder" is actually two years. That means whoever wins in November will have to turn around and run again immediately in 2028 for a full six-year term.

The Bottom Line: What Happens Next?

Here is what I am watching for over the next 10 days. First, watch the fundraising reports. If Hern starts running TV ads next week, he is all in. Second, watch April 1. That is the first day of filing. If Bice files for the Senate, she abandons her House seat. That is a sign of confidence.

As for the placeholder, expect Governor Stitt to announce someone in late April—after the filing deadline closes. He won't want his appointee to influence the primary field.

The question of who will replace Markwayne Mullin is wide open. But for the first time in years, Oklahoma has a competitive, high-stakes primary that will test whether the party wants a wealthy deal-maker, a pragmatic conservative, or a firebrand.

Frequently Asked Questions

Q: Who will replace Markwayne Mullin in the Senate?

A: Governor Stitt will appoint a temporary replacement by late April. However, the permanent replacement will be elected in a special election on November 3, 2025. The leading candidates are Reps. Kevin Hern and Stephanie Bice.

Q: When is Markwayne Mullin up for reelection?

A: He is not. He is resigning on March 31, 2025, to become Homeland Security Secretary. The special election to replace him is November 2025.

Q: Why did Trump fire Kristi Noem?

A: Trump announced she was moving to a new role. However, reports indicate friction over a $200 million ad campaign and controversial statements she made about U.S. citizens killed by federal agents.

Q: Can Governor Stitt appoint himself to the Senate?

A: In theory, yes, but it is highly unlikely. He would have to resign as Governor, and the appointee cannot run in November, making it a dead-end job.