Donald Trump introduced Sen. Jeff Sessions as a supporter to thundering applause in an Alabama stadium in February, surprising many observers as Sessions donned a “Make America Great Again” hat and praised Trump’s political “movement.” Now, Sessions finds himself in a once unlikely position: the potential next chief of the Pentagon.

As one of Trump’s first supporters on Capitol Hill, Sessions (R-Ala.) has positioned himself for a leading role in the president-elect’s administration. Since March, he has led Trump’s national-security committee, relying on both his experience as an Army officer in the 1970s and his time on the Senate Armed Services Committee more recently.

“Sessions is a guy who is going to be able to have his pick of what he wants to do,” said Joe Kasper, a Trump supporter and chief of staff for Rep. Duncan D. Hunter (R.-Calif.), who also endorsed the next president. “Look, it’s a short bench. If you’re looking at early endorsers who also understand the complexities of national defense, there aren’t many, and that’s okay.”

The situation has prompted some officials to question whether some national-security experts who expressed strong opposition to Trump may soften their view and offer to serve in his administration. Others who have been supportive are seen as likely contenders for a job.

Kasper said Hunter and his father, former congressman Duncan L. Hunter (R.-Calif.), also would consider potential defense spots in a Trump administration. The elder Hunter served as chairman of the House Armed Services Committee during the administration of George W. Bush before stepping aside. The younger Hunter served in Iraq and Afghanistan as a Marine Corps officer and succeeded his father in Congress in 2009.

Other candidates discussed include retired Lt. Gen. Michael Flynn, a strong supporter of Trump’s with a background in intelligence, and Stephen J. Hadley, who served as national-security adviser to George W. Bush. Hadley did not endorse Trump, but he refrained from signing a letter in which 90 prominent Republicans with foreign-policy experience rebuked him in March. Federal law states that any nominee for secretary of defense must be out of uniform for at least seven years, eliminating Flynn from contention for that job.

There’s also the possibility that complete outsiders may be tapped for important jobs, in keeping with Trump’s call for change, said retired Army Lt. Gen. Thomas Spoehr, the director of the Center for National Defense at the conservative Heritage Foundation. Whoever serves as a defense official for Trump should focus on how badly the U.S. military’s readiness levels and equipment have deteriorated under the Obama administration, he said.

“It’s a function of damage control,” Spoehr said. “All of the services haven’t even begun to climb out of the depths of the readiness crisis that has been created.”

Sessions, 69, was an active-duty officer for three years at the tail end of the Vietnam War, and he stayed in the Army Reserve as a captain through 1986. He has pressed for a strong defense on Capitol Hill, raising concerns about cuts the Obama administration made to the defense budget and how the country’s national debt could affect national security.

“I am uneasy and very troubled by the fact, it seems to me, that the Defense Department has disproportionately taken reductions,” he said during a Senate Armed Services Committee hearing in 2014. “I’m worried about where we are. I’m worried on what kind of damage this may do to the military.”

Most prominently, Sessions has pressed for a crackdown on immigration, saying he is opposed to any path for legal citizenship for undocumented immigrants and is in favor of Trump’s plan to build a wall on the Southern border.

Sessions also fought unsuccessfully in 2013 to restore about $6 billion in funding to military pensions, offering an amendment that would have instead eliminated money for an Internal Revenue Service credit that undocumented immigrants claimed. The move was blocked by Senate Majority Leader Harry M. Reid (D-Nev.), but the military pension funding was restored a few months later.

Sessions grew up outside Selma, Ala., and rose to prominence in his home state as a prosecutor. His career has been marked by both service to country and allegations of racism. In 1986, he was nominated by President Ronald Reagan to serve as a federal-district court judge, but a bipartisan panel of Judiciary Committee senators declined to send his nomination to the Senate floor amid allegations that he had said the NAACP was “un-American” and “Communist-inspired” and that a white civil rights lawyer was a “disgrace to his race.” Sessions vigorously denied the allegations.

“I am not the Jeff Sessions my detractors have tried to create,” he said. “I am not a racist. I am not insensitive to blacks. I have supported civil rights activities in my state. I have done my job with integrity, equality and fairness for all.”

Sessions recovered politically well enough to be elected as the attorney general in Alabama in 1994 and was elected to the Senate in 1996. He was been reelected three times since, running unopposed in his last election. He is generally considered one of the most conservative senators in the upper chamber, opposing gay marriage, abortion and the legalization of marijuana.

Terry Lathan, the chairwoman of Alabama’s Republican Committee, said that most voters respect Sessions because he is a “rock-solid” conservative who demonstrates consistent decision making. If he’s tapped for an administration position, Republican Gov. Robert J. Bentley would appoint a replacement through 2020, ensuring that the seat remains red.

“I know clearly where Jeff Sessions stands on many, many issues, and that’s one of the reasons why he is so revered in Alabama,” Lathan said. “It will be a sad day for Alabama if he moves on, but if American needs him and needs his talent and heart and patriotism, we would very much support that.”