Oklahoma Governor Stitt Appoints Energy Executive Alan Armstrong to U.S. Senate Seat

Energy executive Alan Armstrong was sworn in as the new Republican senator from Oklahoma on Tuesday, capping a rapid succession that began the night before when the Senate confirmed Markwayne Mullin to lead the Department of Homeland Security in a 54-45 vote.

Gov. Kevin Stitt appointed Armstrong on Tuesday to replace newly confirmed DHS Secretary Markwayne Mullin in the Senate. Armstrong will serve the remainder of Mullin's term until January 2027. Under state law, Stitt had 30 days to appoint someone from Mullin's party to temporarily fill the seat after the senator left his post.

"I'm incredibly proud now to announce that my pick as the next U.S. senator of the state of Oklahoma is Mr. Alan Armstrong," Stitt said at a news conference Tuesday morning. Stitt hailed Armstrong, a third-generation Oklahoman, as a "strong business leader who understands the power of free markets and limited government" and said he is "strongly aligned" with President Trump on energy policy. Stitt said he made his selection after consulting with Trump and Senate leadership in Washington.

Armstrong was appointed to the role of executive chairman of the Williams Companies Board of Directors in July 2025, having transitioned from his long-standing position as president and CEO, a role he held since 2011. Williams accounts for about a third of the natural gas consumed in the United States each day. Armstrong, 63, said he resigned from his position with Williams to take the Senate seat. Stitt noted that Armstrong would have to step down from the board of Williams Companies and "a bunch of different commitments" to serve.

Armstrong has never served in elected office and has spent his career with Williams Companies, which employs about 5,800 people and specializes in the collection, storage and transportation of natural gas. He previously chaired the Department of Energy's National Petroleum Council and is a founding member of Natural Allies for a Clean Energy Future. Armstrong also chairs the board of trustees for the University of Oklahoma Foundation, which manages donations to the state's largest university. He holds a bachelor's degree in civil engineering from OU.

Armstrong said "meaningful permit reform" for all forms of energy will be his priority in the Senate, adding that the country is lagging in large-scale infrastructure growth and that the federal government's permitting process is hindering the country's ability to be competitive. "My short time in the Senate will be tightly focused on meaningful permitting reform to get Americans access to whatever affordable energy solutions they choose," Armstrong said. He told reporters he is ready to support a "Republican agenda" but did not detail his positions on specific policy issues.

Armstrong signed an affidavit required by state law Tuesday morning indicating that he will not run for the seat in 2026, according to a spokesperson for the Governor's Office. Republican U.S. Rep. Kevin Hern quickly announced his candidacy for the Senate seat and has already been endorsed by President Donald Trump.

The Senate confirmed Mullin in a 54-45 vote on Monday, with two Democrats joining Republicans to approve him. Sens. John Fetterman of Pennsylvania and Martin Heinrich of New Mexico voted in favor, while Sen. Rand Paul of Kentucky, who publicly feuded with Mullin at his confirmation hearing, was the lone Republican to vote no. Mullin was sworn in as secretary of the Department of Homeland Security on Tuesday, taking the oath of office at the White House one day after winning confirmation in the Senate.

Oklahoma's senior senator, James Lankford, released a statement welcoming Armstrong to the chamber, saying "Markwayne leaves large boots to fill," but adding he was grateful Armstrong and his family were willing to sacrifice their time to serve, noting that Armstrong brings "real-world experience at a critical time for the American economy."

Armstrong acknowledged the weight of the moment at his announcement. "I will admit to you, I'm a little bit — feel like I'm stepping off into the abyss, with not exactly sure what I'm getting into," he said, adding: "I really do look forward to making a difference for the short time that I'm in the Senate.