President-elect Joe Biden’s historic choice for secretary of defense is running into hurdles on Capitol Hill, as key Democrats express concerns publicly and privately about whether installing a retired four-star general at the helm of the Pentagon further erodes civilian oversight of the military.

Rep. Seth Moulton, an influential member of the House Armed Services Committee, on Wednesday became the most prominent House Democrat to say he will not vote to grant retired Gen. Lloyd Austin a waiver to the law barring recently retired military officers from serving as defense secretary.

“Civilian control of the military is fundamental to our democracy so I don’t think this is the time to make an exception,” Moulton, a Marine veteran of the Iraq War who also ran for president, told POLITICO on Wednesday. “I am taking a vote on principle.”

“Almost by definition a recently retired general is by all intents and purposes thinking like a general,” he added.

Moulton, who has publicly supported former Pentagon policy chief Michèle Flournoy for the job, said the Pentagon needs “a strong, reform-minded leader who is not afraid to tell the military what they may not want to hear.”

A spokesperson for the Biden transition did not immediately comment.

Moulton’s decision comes amid growing concerns among Biden’s advisers that pushing the waiver only four years after one was granted to retired Gen. Jim Mattis will be more difficult than expected, two people familiar with the discussions said.

Several Democratic members who have met with Austin in recent weeks have been underwhelmed, said three other people who are aware of the interactions. They, like the others, spoke on condition of anonymity to discuss private conversations.

One senior Democratic aide attributed Austin’s “growing pains” on Capitol Hill to the initial culture shock of speaking to members as a civilian for the first time, rather than as a high-ranking officer.

“There’s a shift in tone, in expectations, when you show up in your dress uniform with all your sashes and your rank, and when you come in a suit,” the aide said.

However, several senators, including Democratic Whip Sen. Dick Durbin, have released positive statements after meeting with Austin.

The Biden team has brought on a longtime Mattis confidante Sally Donnelly to help Austin with the confirmation process, according to two people familiar with the discussions.

Donnelly, a former journalist who started a consulting firm before serving as a senior adviser to Mattis until 2018, is a volunteer and not part of the transition. She is on a leave of absence from her consulting firm, Pallas Advisors. Donnelly did not respond to a request for comment.

As meetings continue, Austin’s supporters are pushing him to be more cognizant of Democratic concerns over what they consider President Donald Trump’s misuse of the armed forces, and the shift in public perception of the military after its role in the government’s response to protests this summer, according to the aide.

Austin’s backers argue that the retired general understands the importance of civilian control over the military and that his deep experience makes him a fit for the job. They also say that a vote against a waiver, particularly by members who supported one for Mattis, would have a “disparate racial impact.”

One of them, Rep. Anthony Brown of Maryland, who is the only member of the Congressional Black Caucus on the Armed Services Committee, argued that Austin’s experience as the commanding general of all U.S. forces in Iraq demonstrated that he appreciates that civilians get the final word. Austin initially argued for keeping a larger force in the country, yet he carried then-President Barack Obama’s order to draw down.

“When he was in Iraq, he made recommendations to civilian leaders, and not all of those recommendations were accepted, yet he executed,” Brown said. “He’s demonstrated on the other side a real appreciation and understanding that the military provides recommendations and it is civilian leaders who call the shots.”

But Moulton, a Massachusetts Democrat, joins a growing number of Republicans on the House Armed Services panel who also say they won’t vote for a waiver out of concern it would erode civilian control of the military.

Democratic leaders will need to keep their members in line if Republicans oppose the waiver en masse. After a disappointing showing in the 2020 elections, Democrats have a razor-thin House majority, meaning more defections like Moulton’s could spell trouble for passing a waiver if there isn’t bipartisan support for giving Austin the exemption.

Most House Democrats opposed a waiver for Mattis four years ago after the Trump transition team blocked him from testifying before the House Armed Services Committee.

The law prohibits a retired military officer from serving as the top civilian in charge of the armed forces until that person is out of uniform for at least seven years. First adopted when the Department of Defense was established in 1947, the provision was meant to help preserve the doctrine of civilian control of the military enshrined in the Constitution.

Mattis was the only one to be granted such an exception since George Marshall in 1950. Now, the prospect of two recently retired generals leading the Pentagon so close together is giving many lawmakers, including those who backed Mattis, serious misgivings.

The waiver must be approved by the Senate and the House, giving members of the House Armed Services Committee an outsized say. Traditionally only the Senate plays a role in confirming Cabinet nominees.

While the Armed Services panel is planning to take a leading role in the nomination, others have pushed to quickly pass the waiver and effectively bypass the panel. Some Senate Democrats sought to slip the waiver into year-end spending legislation that passed Congress on Monday. The move was supported by some senior House Democrats, including Majority Whip Jim Clyburn, but was ultimately unsuccessful.

Armed Services Committee Chair Adam Smith (D-Wash.) has secured a commitment from the Biden transition that Austin will testify before the House early next year as a condition of the waiver process, a step that might mollify some lawmakers.

“If we want to change the law and lower the timeline then Congress should debate that,” said Moulton, who supported the Mattis waiver. “We shouldn’t be getting into a habit of issuing waivers. A waiver by definition is an exceptional case. That is exactly what we had with President Trump and General Mattis.”

Austin’s congressional backers, meanwhile, are rallying support. On Wednesday, 45 Black, Hispanic and Pacific Islander members of the House urged congressional leaders to “move his nomination and the necessary congressional waiver forward quickly in the 117th Congress.”

“Secretary-designate Austin’s appointment as Secretary of Defense would make our country stronger and safer,” they wrote to House Speaker Nancy Pelosi and Senate Majority Leader Mitch McConnell. “Moreover, as the first Black nominee for Secretary of Defense, Secretary-designate Austin’s appointment would not only break historic barriers, but send an important signal to our country and the rest of the world about the value of diversity, inclusion, sacrifice and strength.”

Meanwhile, the CBC, the NAACP and other prominent Black organizations have publicly thrown their support behind Austin’s nomination.

But warning signs are growing that Austin’s fate in the House, particularly in the influential Armed Services Committee, could face serious obstacles.

“The confirmation process is very different from how they remember it from the early days of Obama,” said one of the people familiar with the discussions. The Biden team “now realizes the waiver is not the cakewalk they thought it would be.”

Some leading hawks on the panel are pressing their colleagues not to grant the waiver when the House gets its chance to vote on the matter in January.

“It was a mistake four years ago and I regret it and I won’t vote for a waiver for Austin,” Rep. Jim Banks of Indiana said in an interview.

Banks said he is circulating to fellow lawmakers an op-ed that appeared in The Wall Street Journal on Sunday by fellow GOP panel member and Marine veteran Mike Gallagher of Wisconsin similarly opposing the waiver.

Other Democrats are also undecided and have expressed reservations about the selection of another recently retired general to run the Pentagon.

Rep. Jason Crow of Colorado, a retired Army officer, said he is eager to hear directly from Austin.

“We have to have that conversation and we have to address concerns about civilian control of the military,” Crow said in an interview. “I think it is important for me to hear directly from General Austin as to how he will address that issue. Civilian control of the military is essential and it is a core component of how we have structured our military.”

Austin’s appearance before the House also needs to address a whole range of questions beyond the waiver, Crow said.

“There are a lot of other really important issues and considerations that we have to take into account,” he said. “It shouldn’t be constrained. The discussion should be very broad. It should include his views of China, the future of warfare, the proper role of the military in democratic society.”

Other Democrats have publicly expressed misgivings over approving another retired general to be Pentagon chief.

Rep. Elissa Slotkin (D-Mich.), another Armed Services member who worked with Austin as a senior Pentagon official during the Obama administration, has said his selection “just feels off."

Slotkin and five other House Democrats have requested a meeting with Austin to address their concerns about civilian control of the military. And in a letter last week they sought a series of assurances to bolster civilian standing in the Pentagon, including by putting qualified civilians in senior policy-making posts and including more senior civilian officials in the most significant departmental decisions.

On the Senate side, where the waiver is seen as more likely to sail through, several Democrats who voted against a waiver for Mattis said they won’t switch votes to help Austin obtain a waiver — including Armed Services members Elizabeth Warren of Massachusetts, Richard Blumenthal of Connecticut, Jon Tester of Montana and Tammy Duckworth of Illinois.

But Duckworth says she will vote to confirm Austin, an indication that, as with Mattis in 2017, a Senate confirmation vote might be wider than a vote for the waiver.

And Moulton said he has spoken to other House Democrats who agree with his position that now is not the time for another waiver.

“A number have said to me privately that’s where they are,” he said.

Tyler Pager and Nolan McCaskill contributed to this report.

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