OKLAHOMA CITY (AP) — President Donald Trump’s plan to nominate U.S. Sen. Markwayne Mullin of Oklahoma as Homeland Security secretary will leave an unexpected Senate vacancy in deep-red Oklahoma.

Under a new Oklahoma law, Gov. Kevin Stitt will get to pick Mullin’s replacement if he does indeed leave his Senate seat. Stitt said in a statement Thursday he will look to appoint “a strong, small government conservative voice to support President Trump.”

Mullin didn’t complete a full six-year term, as he was first elected in 2022 to fill the unexpired term of the late U.S. Sen. Jim Inhofe, who stepped down early.

And whoever Stitt appoints won’t be a U.S. senator for long. The law prohibits that person from running in the next election, which will be held in November, a move that lawmakers said was designed to protect the seat from the advantage of incumbency.

The vacancy for Oklahoma’s U.S. Senate seat is likely to set off a series of political dominoes in the state. Among those who are expected to consider the race are U.S. Reps. Kevin Hern of Tulsa and Stephanie Bice of Oklahoma City, and former Oklahoma House Speaker T.W. Shannon, who Mullin defeated in a GOP runoff in 2022.

Oklahoma’s three-day filing period begins on April 1. Republicans will be heavily favored to retain control of the seat.