Energy executive Armstrong tapped to replace Mullin in Senate – Roll Call

Oklahoma Gov. Kevin Stitt has picked Republican energy executive Alan S. Armstrong to fill the seat former Sen. Markwayne Mullin vacated to serve as President Donald Trump’s new Homeland Security secretary.

Stitt, also a Republican, announced his selection at a Tuesday morning news 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 DHS role. Mullin resigned from his Senate seat immediately after the vote.

Just a few hours after Armstrong’s appointment was announced, he was on the Senate floor, where Senate President Pro Tempore Charles E. Grassley, R-Iowa, administered the oath of office. Armstrong 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.

Armstrong comes to Congress after four decades at Williams, one of the largest natural gas pipeline companies in the United States. The Tulsa businessman 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 Oklahoma State Capitol on 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 in Washington with Trump and Senate leadership, who told him that changes to permitting would be a major priority for the party this year. Armstrong also met with the president 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 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.