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Sen. Markwayne Mullin, R-Okla., was sworn in as the U.S.’ ninth secretary of Homeland Security on Tuesday, with President Donald Trump in attendance.
Mullin, 48, is a former mixed martial arts champion and plumbing business owner who will replace outgoing Secretary Kristi Noem, a South Dakota Republican recently picked to lead the Shield of the Americas security initiative announced by Trump earlier this month.
Mullin will take the reins of DHS at a time of increased turmoil and congressional scrutiny at the agency, where Democrats continue to withhold funding for TSA and other subagencies in hopes of forcing changes to immigration enforcement operations at ICE and CBP.
Sen. Markwayne Mullin, R-Okla., President Donald Trump’s pick for Homeland Security secretary, is sworn in before testifying during Senate Committee on Homeland Security and Governmental Affairs hearing, Wednesday, March 18, 2026 on Capitol Hill in Washington. (Manuel Balce Ceneta/AP)
He narrowly made it through the nomination process after clashing with Senate Homeland Security Committee Chairman Rand Paul, R-Ky., as the two continue to feud over Mullin’s response to an incident in which Paul’s neighbor blindsided him in his yard, fracturing his ribs.
Mullin needed a Democratic ally to get his nomination out of committee after Paul’s no vote. Sen. John Fetterman, D-Pa., who formerly exchanged endorsements with socialist Sen. Bernie Sanders, I-Vt., as Pennsylvania’s lieutenant governor, has become somewhat of a political maverick and provided the necessary vote to advance the nomination to the full Senate.
There, he garnered support from another Democrat, New Mexico Sen. Martin Heinrich, who said in a statement that he doesn’t believe Mullin will be “bullied” or allow himself to “take orders from Stephen Miller” at the White House.
“This is going to surprise some people, but I consider Markwayne Mullin a friend. We have a very honest and constructive working relationship. We have authored legislation together, such as the Tribal Buffalo Management Act, and we crafted the Legislative Branch Appropriations bill together this year,” Heinrich said.
“We often disagree and when we do, we work to find whatever common ground we share.”
In turn, Oklahoma Gov. Kevin Stitt was tasked with naming Mullin’s replacement, which was subject to a unique Sooner State law that requires the nominee to pledge not to run for a full term in the Senate come November.
Stitt named natgas magnate Alan Armstrong, chief executive of the Williams Companies, whose nomination was criticized by some on the right given the mogul’s past donations to then-Rep. Adam Kinzinger, R-Ill., a vocal Trump critic.
“He’s a strong business leader who understands the power of free markets and limited government. He spent his career fighting for Oklahoma’s energy industry and providing affordable, reliable energy to all of America,” Stitt said of Armstrong on Tuesday.
Mullin succeeds Noem, who herself succeeded controversial Secretary Alejandro Mayorkas, whom Trump blamed for the open border crisis.
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Other top names who have held the role include its inaugural secretary, former Pennsylvania Gov. Tom Ridge, nominated by President George W. Bush in the wake of 9/11. Ridge has since broken with the mainstream “MAGA” GOP in his support for Trump.
Former Arizona Gov. Janet Napolitano, former Air Force general counsel Jeh Johnson, Gen. John Kelly (Ret.), and former Deputy Trump White House chief of staff Kirstjen Nielsen also prominently served.