Senator James M. Inhofe, Republican of Oklahoma, has told officials in his state that he will step down at the end of this Congress, vacating a seat he has held since 1994 with four years remaining in his term.
Mr. Inhofe, 87, was poised to announce his plans on Monday, according to two Oklahoma Republicans who spoke on the condition of anonymity because they were not authorized to comment in advance. His retirement is unlikely to affect the balance of power in the 50-50 Senate, given Oklahoma’s solidly Republican leanings.
A conservative and the top Republican on the Armed Services Committee, Mr. Inhofe has cruised to re-election, most recently in 2020.
While he is expected to leave his seat well before his term expires at the beginning of 2027, Mr. Inhofe is not planning to quit before the end of this year, he has told people. By announcing his intention next week, he will assure that he can be replaced in a special election in November.
That is because, under a new state law in Oklahoma, if Mr. Inhofe waited beyond March 1 to announce his resignation, the special election to replace him would not take place until 2024. And if he were to resign immediately, his seat would be temporarily filled by the governor.
Instead, Mr. Inhofe’s announcement is expected to fire the starting gun on a wide-open dash to be his successor, a race that will most likely be decided in the Republican nominating contest.
Potential G.O.P. candidates to succeed him include Matt Pinnell, the state’s lieutenant governor; T.W. Shannon, the former speaker of the Oklahoma House of Representatives; and R. Trent Shores, a former U.S. attorney in the state. Other possible contenders include Luke Holland, Mr. Inhofe’s chief of staff, and most members of Oklahoma’s House delegation.
Mr. Inhofe’s career tracked his state’s political realignment. He was first elected to the State Legislature in 1966, but lost bids for Congress and governor in the 1970s, when Oklahoma was still dominated by moderate Democrats. It was not until 1986 that Mr. Inhofe won a seat in the House and, fittingly, he claimed his Senate seat in 1994, a landslide election for Republicans nationally and a watershed year in Oklahoma marking the state’s shift to the G.O.P.
A stalwart of the ideological right, he has a penchant for grand gestures to make a point. Mr. Inhofe flew a plane upside down in a re-election advertisement in 2020 to show he was still fit for office even in his mid-80s. In 2015, when he was the chairman of the Environment and Public Works Committee, he threw a snowball across the Senate floor in an attempt to undermine the validity of climate science.
Mr. Inhofe has been vociferous in his support for a muscular American military presence around the globe. Intent on increasing the nation’s defense budget, he is seen as a hawkish guardian of one of Congress’s key responsibilities: passing the annual defense policy bill. In 2020, he led his party in a rare break from President Donald J. Trump to pass the crucial legislation over the president’s objections.
Catie Edmondson contributed reporting.