Energy executive Armstrong tapped to replace Mullin in Senate

Nick Eskow, CQ-Roll Call on Mar 24, 2026

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WASHINGTON — Oklahoma Gov. Kevin Stitt named Republican energy executive Alan S. Armstrong to the Senate, filling the vacant seat left by the resignation of former GOP Sen. Markwayne Mullin to serve as President Donald Trump’s next Homeland Security secretary.

Stitt, also a Republican, announced his selection at a Tuesday morning press conference, calling Armstrong a “strong business leader” and a champion of the state’s energy industry.

“Alan is strongly aligned with President Trump on energy policy. Few people have done more to champion the America-first agenda to keep Oklahoma at the center of domestic energy production,” Stitt said.

The announcement came the morning after the Senate voted 54-45 to confirm Mullin for the role. Mullin resigned from his Senate seat immediately after the vote.

Armstrong is expected to take the Senate oath of office Tuesday afternoon. He will serve the remainder of Mullin’s unexpired term, which ends in January 2027. Under state law, Armstrong cannot run for a full term. Trump has already endorsed Rep. Kevin Hern, R-Okla., in advance of the June primary in the race for a full Senate term.

The Tulsa businessman comes to Congress after four decades at Williams, one of the largest natural gas pipeline companies in the U.S. He spent 14 years as CEO before being named chairman of the board in 2025. Armstrong joined the company in 1986 as an engineer.

Armstrong resigned from his board seat ahead of his Senate appointment. He also previously served on the board of the American Petroleum Institute and was a member of the President’s National Infrastructure Advisory Council under President Joe Biden.

Speaking to reporters at the state capital Tuesday morning, Armstrong said his top priority for Congress will be overhauling the permitting process for infrastructure projects, particularly 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.

Stitt said he chose Armstrong after meeting with President Donald Trump and Senate leadership in Washington, who told him that changes to permitting would a major priority for the party this year. Armstrong also met with Trump ahead of his appointment.

“To me it was a nonpolitical pick,” Stitt said. “It was the pick that I thought was going to serve our country the best.”

A third-generation Oklahoman, Armstrong grew up near Bartlesville, where his grandfather worked at ConocoPhillips. He holds a bachelor’s degree in civil engineering from the University of Oklahoma.

Armstrong said taking the Senate appointment feels “a little bit like I’m stepping off into the abyss,” but that he intends to work closely with Senate Republican leaders to advance his energy priorities and the party’s broader agenda.

“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.