No one has officially replaced Sen. Markwayne Mullin in the U.S. Senate yet, but we do know the process and the early maneuvering for his soon‑to‑be‑vacant Oklahoma seat.

What just happened to Markwayne Mullin?

  • President Donald Trump has announced that Oklahoma Sen. Markwayne Mullin will become the new Secretary of Homeland Security, replacing Kristi Noem.
  • Trump said Mullin will take over at DHS effective March 31, 2026, pending Senate confirmation.
  • Once he formally leaves the Senate to join the cabinet, his Oklahoma seat becomes vacant.

So the “who will replace Markwayne Mullin” question is really about who gets his Oklahoma Senate seat after he moves to DHS.

How Mullin’s Senate seat will be filled

Oklahoma law spells out a two‑step process.

  1. Temporary appointment by the governor
    • State law allows Governor Kevin Stitt to appoint a temporary replacement within 30 days of Mullin’s seat becoming officially vacant.
 * That appointee serves only until the next general election, set for November 3, 2026.
  1. Election for the rest of the term
    • The permanent replacement will be chosen by voters in that November 2026 election.
 * Given Oklahoma’s strong Republican lean, most analysts expect the seat to remain with the GOP, though that is ultimately up to voters.

At this point, the governor has not publicly named a specific appointee, so there is no confirmed individual filling Mullin’s seat yet.

Who are the likely contenders?

Reports describe a “mad dash” starting inside Oklahoma Republican politics as people position themselves for Mullin’s seat, but most detailed lists are behind paywalls or still speculative.

Based on what’s publicly available and typical Oklahoma politics dynamics:

  • Current or former statewide officials are natural possibilities (e.g., lieutenant governor, statewide officeholders) because they already have name recognition and donor networks.
  • Prominent GOP members of Congress from Oklahoma (House members) are also logical contenders if they want to move up to the Senate.
  • Well‑connected state legislators or business figures with strong ties to the state party and to Trump‑aligned networks could be considered for the temporary appointment, even if they are not yet widely known nationally.

However, as of early March 2026, no single name has been officially anointed or confirmed by Governor Stitt, and public reporting focuses more on the process than on a definitive frontrunner.

What we can and cannot say right now

What we can say with confidence:

  • Mullin is slated to become Secretary of Homeland Security, replacing Kristi Noem.
  • His departure will open a Senate vacancy in Oklahoma.
  • Governor Kevin Stitt can appoint a temporary senator within 30 days of the vacancy.
  • Voters will choose the longer‑term replacement in the November 3, 2026 general election.

What we cannot honestly say yet:

  • A specific, official name of “the person who will replace Markwayne Mullin” in the Senate, because no appointment has been announced and no election has occurred.

So, the accurate answer right now is:

The person who will replace Markwayne Mullin in the U.S. Senate has not yet been formally chosen. Oklahoma’s governor will first appoint a temporary replacement, and voters will then pick a longer‑term successor in the November 2026 election.

Bottom note: Information gathered from public news and political reporting available on the internet and portrayed here.