Kevin Hern jumps into Oklahoma Senate race as Mullin heads to DHS

House GOP Policy Committee Chairman Kevin Hern is officially launching a campaign for the U.S. Senate seat being vacated by Sen. Markwayne Mullin, making him the first major Republican candidate to declare his intent to run for the seat in November. Mullin is expected to leave the upper chamber after President Trump tapped him to lead the Department of Homeland Security.

Hern, a member of House GOP leadership who has represented Oklahoma since 2018, wasted no time framing the race in unmistakable terms.

"The American dream is under threat by the radical left and RINO Republicans who oppose President Trump's America First agenda and want to turn the United States into a third-world country."

That's the kind of opening salvo that tells you a candidate isn't running to warm a seat. He's running to hold a line.

A Senate Seat Built for a Fight

Hern positioned his candidacy squarely as a continuation of the Trump agenda, pledging loyalty not as a talking point but as a track record, according to Fox News. His full announcement laid out exactly what Oklahoma voters should expect.

"That's why I'm running for U.S. Senate — to ensure President Trump has a loyal ally, a leader who stood by his side when RINOs turned their backs on him, who will fight against Democrat insanity, keep the southern border secure, deport dangerous illegal immigrants, stand with law enforcement, and deliver economic affordability."

The emphasis on border security and deportation isn't incidental. Hern is running to replace the man Trump chose to run DHS. That's a signal about what Oklahoma's next senator will be expected to deliver on. Immigration enforcement isn't just a campaign plank here. It's the connective tissue between Mullin's departure and Hern's entrance.

Hern also brought serious firepower to his launch, recruiting pollster Tony Fabrizio as his campaign's senior advisor. Fabrizio said in a statement that Hern is in a "strong position" to win, citing his "record of support for President Trump's agenda, the trust he has built with Oklahoma voters, and his experience in public service and in business."

He's also already locked down endorsements from at least four sitting Republican senators:

• Sen. Jim Banks, R-Ind.
• Sen. Bill Hagerty, R-Tenn.
• Sen. Rick Scott, R-Fla.
• Sen. Ron Johnson, R-Wis.

That's not a soft launch. That's a campaign that arrived with infrastructure already in place.

The Confirmation Clock

Mullin is set to begin his confirmation process in the upper chamber next week, with a hearing before the Senate Homeland Security and Governmental Affairs Committee expected later this month. He is widely expected to pass through committee without significant resistance. Whether he hits hurdles during a full confirmation vote remains an open question, but the timeline is moving fast.

Trump has given a deadline of March 31 for Mullin to take over at DHS and for Kristi Noem to exit. That's not a suggestion. It's a marker that the administration wants this transition completed and the new DHS leadership operational before spring.

Senate Majority Leader John Thune made clear the caucus is moving with urgency on the vacancy side as well.

"You know, obviously we want — we're going to have to fill that seat for Markwayne here by the end of the month in the near term, and then the long-term issue will be decided by the voters of Oklahoma."

Thune said he has no preference on who fills the seat and added, "So whoever they decide to send us, we'll be happy to receive." He is also set to meet with Oklahoma Gov. Kevin Stitt this week, according to a source familiar with the plans.

Oklahoma's Unique Rules Shape the Race

Here's where it gets interesting. Traditionally, Senate vacancies are filled by the state's governor to serve out the remainder of the previous senator's term. But in Oklahoma, the governor's appointee must sign an affidavit swearing they will not run in the next election.

That creates a clean separation between the interim appointment and the November race. Whoever Stitt appoints to keep the seat warm through the end of 2026 cannot be the same person who runs to hold it permanently. The appointment is a placeholder. The real contest plays out at the ballot box.

This means Hern's early entrance carries real strategic weight. He doesn't have to worry about running against an incumbent appointee with the advantages of office. Every declared candidate starts from the same position. First mover advantage, combined with Senate endorsements and a seasoned campaign advisor, gives Hern significant early leverage.

Rep. Stephanie Bice, also a Republican from Oklahoma, has said she is considering her own campaign but has not made any final decisions. If she enters, the primary becomes a genuine contest. If she doesn't, Hern's lane to the nomination widens considerably.

What This Race Is Really About

Oklahoma is not a battleground state. The question here isn't whether a Republican wins the seat. It's which kind of Republican wins it. Hern has made his bet clear: this is a race about alignment with the America First agenda, about border enforcement, about standing firm when the easy play is to equivocate.

The fact that this seat opens because Trump pulled Mullin into the cabinet tells you everything about the stakes. The president needs allies at DHS who will execute, and he needs allies in the Senate who will confirm, fund, and defend that execution. Hern is positioning himself as the second half of that equation.

Oklahoma voters will decide whether he's earned it. But the race is on, and the first candidate out of the gate arrived with a clear message, serious backing, and zero ambiguity about where he stands.