No one has officially replaced Senator Markwayne Mullin yet, but the process and likely contenders are already clear based on current reporting.

Quick Scoop: What’s Happening With Mullin’s Seat?

Sen. Markwayne Mullin of Oklahoma is expected to leave the Senate to become Secretary of Homeland Security in President Donald Trump’s administration, replacing Kristi Noem. His resignation is expected around March 31, 2026, which triggers both a temporary appointment and a special election.

How the Replacement Works

  • Oklahoma law gives Governor Kevin Stitt the power to appoint an interim U.S. senator once Mullin resigns.
  • That appointee must sign an affidavit promising not to run in the November election for the full term.
  • A special election will follow, with the primary reportedly set for mid-June and a filing deadline in early April.
  • The interim senator will just be a short‑term placeholder until voters pick a long‑term replacement in November.

So there will be two stages: a temporary appointee, then an elected successor.

Who Might Run for Mullin’s Seat?

No successor has been chosen yet, but several Oklahoma Republicans are already signaling interest or being floated as likely candidates.

Names mentioned in current coverage include:

  • Rep. Stephanie Bice
    • Oklahoma City–area House member, publicly acknowledging she’s “carefully considering” a Senate bid after encouragement from around the state.
  • Rep. Kevin Hern
    • Tulsa‑area congressman, frequently cited as “almost certain” to run and widely rumored as a top contender.
  • Other Republicans being floated
    • Rep. Josh Brecheen (another Oklahoma House member).
* Lt. Gov. Matt Pinnell.

* Former Tulsa Mayor G.T. Bynum.

* Former state GOP Chair Nathan Dahm.

At this point, these are potential and rumored candidates; the actual primary lineup will only be clear after the filing deadline passes in early April.

What About the Temporary Appointee?

So far, reporting focuses more on the election than on specific names for the short‑term appointee. A few key points:

  • Gov. Stitt has up to 30 days after the vacancy to name an interim senator from Mullin’s party.
  • That person cannot, by law, run for the full term this November, which makes the appointment more of a caretaker role.
  • House Speaker Mike Johnson has said that Stitt promised not to pull a sitting House Republican for the temporary slot, because the House majority is tight and “we can’t lose anyone.”

Given those constraints, observers expect a lower‑profile Republican or elder statesperson rather than one of the ambitious figures eyeing a full six‑year term.

Political Stakes and Speculation

From a political angle:

  • Oklahoma is a solidly Republican state, so the eventual winner is expected to be a Republican, barring a major upset.
  • The real drama will likely be in the GOP primary between figures like Bice, Hern, and possibly other statewide names.
  • Because the interim appointee is barred from running in November, the person who “replaces Senator Mullin” in the long run will almost certainly come out of that Republican primary and the November special general election.

Short answer to your core question

  • Who will replace Senator Mullin?
    • Temporarily: An as‑yet‑unnamed Republican appointee chosen by Gov. Kevin Stitt, serving only until January 2027.
* Long term: Most likely the winner of a 2026 special election, with current buzz centering on Republicans Stephanie Bice and Kevin Hern, plus a handful of other potential GOP contenders.

Information gathered from public forums or data available on the internet and portrayed here.