Oklahoma Gov. Kevin Stitt is expected to appoint Williams Companies chairman Alan Armstrong to the U.S. Senate seat currently held by Sen. Markwayne Mullin, as Mullin moves closer to confirmation as Secretary of Homeland Security.

Stitt has selected Armstrong, a longtime Tulsa-based energy executive, to fill the seat on an interim basis. The appointment would take effect if Mullin is confirmed to replace former Homeland Security Secretary Kristi Noem under President Donald Trump.

The Senate voted 54-37 on Sunday to advance Mullin’s nomination, with two Democrats joining Republicans in support. A final confirmation vote is expected in the coming days.

Armstrong, chairman of Williams Companies, would serve until the next election, when Oklahoma voters will choose who completes the remainder of the term. The Tulsa-based firm is a major natural gas infrastructure company operating in more than 25 states.

With nearly four decades at Williams, including over a decade as CEO, Armstrong brings experience in energy production, pipeline infrastructure, and regulatory policy. He has advocated for expanding domestic energy development and increasing pipeline capacity to meet rising demand.

Stitt reportedly considered multiple candidates, including advisor Dustin Hilliary and energy executive Harold Hamm, but Armstrong emerged as the leading choice due to his industry expertise.

If confirmed, Mullin’s move to the Department of Homeland Security and Armstrong’s appointment would reshape Oklahoma’s representation in Washington and could influence ongoing energy policy debates.