Mullin tapped for DHS; cannot keep Senate seat

OKLAHOMA CITY (OBV) — President Donald Trump said Thursday he will nominate U.S. Sen. Markwayne Mullin to serve as Secretary of Homeland Security, with an effective date of March 31, 2026. “I am pleased to announce that the highly respected United States Senator from the great state of Oklahoma, Markwayne Mullin, will become the United States Secretary of Homeland Security,” Trump wrote.

Under the Incompatibility Clause of the U.S. Constitution, no person may be a member of either House of Congress while holding an “Office under the United States.” If Mullin is confirmed and sworn in at DHS, he must resign his Senate seat.

“Markwayne Mullin has been a fighter for Oklahoma and will fight to keep our nation secure. There isn’t a better choice to lead the Department of Homeland Security. Oklahoma has been an example to the nation for smart immigration enforcement, and Markwayne will bring that common sense to DHS. I will be looking to appoint a strong, small government conservative voice to support President Trump and protect Oklahomans’ way of life,” said Governor Kevin Stitt.

State process: Oklahoma law requires the Governor to appoint a same‑party interim senator within 30 days of the vacancy. The appointee must take an oath not to run for the seat in the ensuing election.

Ballot mechanics: Because Mullin’s Class II seat is already on the 2026 ballot, the state does not run a separate special election. Instead, the winner of the regularly scheduled 2026 election is deemed also elected to fill the unexpired term and may take office upon certification of the November results.

Mullin’s current term runs through January 3, 2027; he is up for reelection this year.

The upshot: If confirmed, expect a quick resignation, a GOP placeholder, and then the certified 2026 winner stepping in early to finish the term.