Oklahoma Governor Names Energy Executive to Fill DHS Secretary Markwayne Mullin’s Senate Seat

Energy executive Alan Armstrong has been picked by Oklahoma Gov. Kevin Stitt to fill the unexpired term of former Republican Sen. Markwayne Mullin, now that Mullin has been confirmed as the secretary of the Department of Homeland Security.

“He’s a strong business leader who understands the power of free markets and limited government,” Stitt said, according to WTOP-TV. Armstrong had been the board chairman and former CEO of Williams Companies, a Tulsa-based pipeline operator.

Oklahoma law prevents Armstrong from running in November’s election, when Mullin’s seat would have been up for grabs.

“Alan is strongly aligned with President Trump on energy policy,” Stitt said, according to KATV-TV.

“Few people have done more to champion America First agenda to keep Oklahoma at the center of domestic production so that we can deliver clean, reliable, and affordable energy to American citizens than Alan Armstrong,” he said.

“This was definitely a tough decision on one hand, but on the other hand it was kind of a no-brainer because I really wouldn’t wanna be sitting around in my retirement thinking, ‘Gosh, I could have contributed and done something,’” Armstrong said.

Sen. Alan Armstrong (R-OK) is sworn into the U.S. Senate. pic.twitter.com/e1S565Ogtk

— CSPAN (@cspan) March 24, 2026

Although Armstrong’s appointment was announced Tuesday morning, by afternoon, he had been sworn in, according to Roll Call.

Before leaving for Washington, Armstrong said he wanted to reform the process for getting federal permits for energy infrastructure.

“The truth is, it’s gotten very, very hard to build large-scale infrastructure, and it is so critical to our country’s competitiveness in the long term. … It’s hard for any kind of infrastructure to get built, and that really is holding our country back,” Armstrong said.

Armstrong said entering the Senate is “a little bit like I’m stepping off into the abyss.”

“I’ve got a lot of learning to do, but I’m going to be listening to people that I have a lot of respect for,” he said.

Even before Mullin’s appointment was confirmed, Trump had supported Republican Rep. Kevin Hern of Oklahoma to fill the seat left vacant.

“Kevin Hern, from the Wonderful State of Oklahoma (where I won all 77 out of 77 Counties, in 2016, 2020, and 2024!), is a Great Patriot, and FANTASTIC Congressman! A true friend of MAGA, Kevin is now running for the United States Senate, where I know he will continue to do an incredible job,” Trump posted on .

.@repkevinhern is a strong conservative who’s delivered for Oklahoma families & fought to make America safer and more prosperous.

We need Kevin’s leadership in the Senate where he will be a powerful voice for conservative values.

Support Kevin here: https://t.co/YYZyhKShbo

— Tom Cotton (@TomCottonAR) March 20, 2026

“Kevin is strongly supported by the fiercest MAGA Warriors in Oklahoma, and the most Highly Respected Leaders in the United States Senate! As the Chair of the House Republican Policy Committee, Kevin is doing a tremendous job advancing our AMERICA FIRST Agenda,” Trump wrote.

“In the U.S. Senate, Kevin will continue to fight tirelessly to Grow our Economy, Cut Taxes and Regulations, Champion our Amazing Farmers and Ranchers, Promote MADE IN THE U.S.A., Ensure American Energy DOMINANCE, Keep our Border SECURE, Strengthen our Military/Veterans, Safeguard our Elections, and Protect our always under siege Second Amendment,” Trump wrote.

“Kevin Hern will be an outstanding Senator, and has my Complete and Total Endorsement – HE WILL NEVER LET YOU DOWN!” Trump wrote.

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