--- title: Who Is Replacing Markwayne Mullin in the Senate? description: A temporary replacement for the outgoing Oklahoma Senator has been chosen, and the campaign for his seat is underway. canonical: https://time.com/article/2026/03/24/markwayne-mullin-senate-oklahoma-alan-armstrong/ author: Connor Greene article:opinion: false article:content_tier: free article:published_time: 2026-03-24T20:05:19.092Z article:modified_time: 2026-03-24T20:05:29.853Z article:section: Politics og:title: Who Is Replacing Markwayne Mullin in the Senate? og:description: A temporary replacement for the outgoing Oklahoma Senator has been chosen, and the campaign for his seat is underway. og:url: https://time.com/article/2026/03/24/markwayne-mullin-senate-oklahoma-alan-armstrong/ og:site_name: TIME og:image: https://static.time.com/v3/assets/bltea6093859af6183b/blt02d7a1272bacf951/69c2dd33139501ff6c1c4c12/GettyImages-2264636735.jpg?branch=production&width=2400&quality=75&auto=webp&crop=16:9 og:image:width: 1200 og:image:height: 675 og:image:alt: GettyImages-2264636735.jpg og:type: article twitter:card: summary_large_image twitter:title: Who Is Replacing Markwayne Mullin in the Senate? twitter:description: A temporary replacement for the outgoing Oklahoma Senator has been chosen, and the campaign for his seat is underway. twitter:image: https://static.time.com/v3/assets/bltea6093859af6183b/blt02d7a1272bacf951/69c2dd33139501ff6c1c4c12/GettyImages-2264636735.jpg?branch=production&width=2400&quality=75&auto=webp&crop=16:9 ---  # Who Is Replacing Markwayne Mullin in the Senate? ## Video: The Big Challenges Facing Trump’s DHS Nominee [Watch (HLS stream): The Big Challenges Facing Trump’s DHS Nominee](https://cdn.jwplayer.com/manifests/gU2NxZ3P.m3u8) (1:32)  _Published 2026-03-18. A temporary replacement for the outgoing Oklahoma Senator has been chosen, and the campaign for his seat is underway._ by [Connor Greene](https://time.com/author/connor-greene/) ## Connor Greene Editorial Fellow Mar 24, 2026 8:05 PM UTC by [Connor Greene](https://time.com/author/connor-greene/) ## Connor Greene Editorial Fellow Mar 24, 2026 8:05 PM UTC With [Markwayne Mullin](https://time.com/7382769/markwayne-mullin-homeland-security-secretary-kristi-noem/) leaving the Senate to serve as the new [Secretary of Homeland Security](https://time.com/7382975/kristi-noem-new-job-shield-of-americas/), a temporary replacement has been tapped to fill his seat until an election for his successor is held in the fall. On Tuesday, Oklahoma Gov. Kevin Stitt [announced](https://x.com/GovStitt/status/2036456692548816968) he was appointing energy executive Alan Armstrong to step into the Senate vacancy left by Mullin after the Oklahoma senator was confirmed to his new position in the Trump Administration the previous night. Armstrong, like Mullin, is a Republican, meaning the balance of power in the Senate will not shift. “Alan is a proud third-generation Oklahoman, staunch conservative, respected business leader, and a devoted family man with an inspiring American Dream story,” Stitt wrote in a post on X. **Read more:** [_Markwayne Mullin Confirmed as Homeland Security Secretary Amid Standoff Over Immigration Enforcement_](https://time.com/article/2026/03/23/mullin-dhs-confirmed-senate-shutdown-noem-tsa-ice/) Armstrong will remain in the position until a new Senator is elected in November to serve a full six-year term. He is barred under Oklahoma law from running for the seat himself. Here’s what to know about Armstrong, and the leading candidate in the fall election. ## **Who is Alan Armstrong?** Armstrong, 63, was the Executive Chairman of [Williams Companies](https://www.williams.com/#:~:text=Williams%20is%20an%20energy%20infrastructure%20company%20that,%2A%2ALeading%20the%20industry%2A%2A%20Scale%2C%20reach%2C%20and%20reliability), a natural gas company based out of Tulsa, Oklahoma. Williams handles roughly a third of the natural gas consumed in the U.S. through its pipeline infrastructure, according to the company. Prior to stepping into his current role at the company last July, Armstrong served as the CEO of Williams for nearly 15 years. “He is entering the U.S. Senate at a critical time for advancing reforms to secure America’s energy future,” Stitt said on X on Tuesday. “I have no doubt that his perspective will be influential in moving the needle on permitting reform to unlock American competitiveness and energy affordability for generations to come.” Armstrong said during a news conference following his appointment that he has previously worked with Secretary of Interior Doug Burgum and Secretary of Energy Chris Wright, connections he said he believes helped him earn Trump’s support. He described having a “great” and “very interesting” meeting with the President. “Those gentlemen know how hard I’ve been working to get permitting reform done, so \[Trump\] was very welcoming and highly supportive,” Armstrong said. Armstrong has also long backed Stitt. In 2018, the year the governor was elected to his first term, Armstrong contributed $8,500 to his campaign, according to [The Associated Press](https://apnews.com/article/us-senate-oklahoma-markwane-mullin-alan-armstrong-ee9c0bce4950de2137a5870b5bd13ce5), the highest amount permitted by Oklahoma law. Armstrong admitted during the news conference that he felt a bit like he was “stepping off into the abyss” and was “not entirely sure what I’m getting into.” “But I’m confident,” he said, “got great team around me, and great support around me, and I really do look forward to making a difference for the short time that I’m in the Senate.” ## **Who will win Mullin’s seat in November?** The Oklahoma primary election will take place on June 16, and candidates must officially file to run during a three day period from April 1-3\. The general election is on November 3. Republican Rep. Kevin Hern of Oklahoma has emerged as the leading candidate in the race. After Trump named Mullin as his pick to replace Kristi Noem as Homeland Security Secretary earlier this month, Hern and another Oklahoma Republican in the House, Rep. Stephanie Bice, were both quick to say they were weighing bids for his seat. But [Bice](https://x.com/stephaniebice/status/2032456653128294741?s=46) later said she would opt to seek re-election in the House instead. [Stitt](https://www.news9.com/oklahoma-city-government-and-politics/gov-kevin-stitt-says-he-will-not-run-for-u-s-senate-plans-to-finish-governors-term) also confirmed that he would not be running, leaving the Republican field largely clear for Hern. “I grew up on an Air Force base, worked my way through school, built businesses, and served Oklahoma in Congress. Now I’m ready to fight for Oklahoma in the Senate,” Hern wrote in a [post](https://x.com/krhern/status/2031777176572272855?) on X when announcing his campaign. **Read more:** [_Democrats See Narrow Path to Winning Senate Control. Here Are the Races to Watch_](https://time.com/7357434/democrats-2026-elections-senate-races-donald-trump-texas-maine-michigan/) Hern has secured several key endorsements from his [Republican](https://punchbowl.news/article/senate/hern-hill-endorsements/) [colleagues](https://thehill.com/homenews/campaign/5792363-oklahoma-senate-race-endorsements/) in Congress—and from the President. “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 said in a Truth Social [post](https://truthsocial.com/@realDonaldTrump/posts/116224634088762061) from March 13, offering Hern his “Complete and Total Endorsement.” “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.” Hern [thanked Trump](https://x.com/krhern/status/2032612779769594111) for his endorsement on X and said that he is “eager to continue to be an ally for him in the Senate” and “proud to stand with him to secure our borders, strengthen our economy, support our men and women in uniform, and restore the American Dream for hardworking families.” Whoever wins the Republican primary is likely to win in November as well. It has been decades since Oklahoma last elected a Democrat to the Senate. The [Cook Political Report](https://www.cookpolitical.com/ratings/senate-race-ratings) rates Mullin’s seat Solid Republican, among the races expected to be the least competitive this year. ```json [{"@context":"https://schema.org","@type":"NewsArticle","@id":"https://time.com/article/2026/03/24/markwayne-mullin-senate-oklahoma-alan-armstrong/","mainEntityOfPage":{"@type":"WebPage","@id":"https://time.com/article/2026/03/24/markwayne-mullin-senate-oklahoma-alan-armstrong/"},"headline":"Who Is Replacing Markwayne Mullin in the Senate?","datePublished":"2026-03-24T20:05:19.092Z","dateModified":"2026-03-24T20:05:29.853Z","description":"A temporary replacement for the outgoing Oklahoma Senator has been chosen, and the campaign for his seat is underway.","url":"https://time.com/article/2026/03/24/markwayne-mullin-senate-oklahoma-alan-armstrong/","keywords":["Congress","News Desk","elections"],"thumbnailUrl":"https://static.time.com/v3/assets/bltea6093859af6183b/blt02d7a1272bacf951/69c2dd33139501ff6c1c4c12/GettyImages-2264636735.jpg?branch=production&width=1200&quality=75&auto=webp&crop=1200:675&height=675","author":[{"@type":"Person","name":"Connor Greene","jobTitle":"Editorial Fellow","url":"https://time.com/author/connor-greene/"}],"articleSection":"Politics","image":[{"@type":"ImageObject","url":"https://static.time.com/v3/assets/bltea6093859af6183b/blt02d7a1272bacf951/69c2dd33139501ff6c1c4c12/GettyImages-2264636735.jpg?branch=production&width=1200&quality=75&auto=webp&crop=1200:675&height=675","width":1200,"height":675,"headline":"GettyImages-2264636735.jpg","caption":"","creditText":"","representativeOfPage":true}],"publisher":{"@type":"Organization","name":"Time","url":"https://time.com/","logo":{"@type":"ImageObject","url":"https://time.com/images/logo.png","width":528,"height":156},"foundingDate":"March 3, 1923","sameAs":["https://www.facebook.com/time","https://www.instagram.com/time/?hl=en","https://twitter.com/time","https://www.pinterest.com/timemagazine"]}},{"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"item":{"@id":"/section/politics/","name":"Politics"}},{"@type":"ListItem","position":2,"item":{"@id":"/tag/congress/","name":"Congress"}},{"@type":"ListItem","position":3,"item":{"@id":"https://time.com/article/2026/03/24/markwayne-mullin-senate-oklahoma-alan-armstrong/","name":"Who Is Replacing Markwayne Mullin in the Senate?"}}]},{"@context":"https://schema.org","@type":"VideoObject","name":"The Big Challenges Facing Trump’s DHS Nominee","description":"A temporary replacement for the outgoing Oklahoma Senator has been chosen, and the campaign for his seat is underway.","thumbnailUrl":"https://cdn.jwplayer.com/v2/media/gU2NxZ3P/poster.jpg?width=720","uploadDate":"2026-03-18T21:12:03.000Z","contentUrl":"https://cdn.jwplayer.com/manifests/gU2NxZ3P.m3u8","embedUrl":"https://time.com/article/2026/03/24/markwayne-mullin-senate-oklahoma-alan-armstrong/","duration":"PT1M32S","potentialAction":{"@type":"SeekToAction","target":"https://time.com/article/2026/03/24/markwayne-mullin-senate-oklahoma-alan-armstrong/?jw_start={seek_to_second_number}","startOffset-input":"required name=seek_to_second_number"}}] ```