The appointment this week of Matthew Whitaker as acting attorney general has sparked sharp concerns among lawmakers over the possibility that he may bottle up Special Counsel Robert Mueller’s investigation into Russia meddling in the 2016 election.

Inside the Department of Justice, however, the fears are more expansive. Whitaker is seen as a rogue and under-qualified new leader whose impact won’t just be felt on the Mueller probe but throughout the federal government.

“He’s a fucking fool,” one trial attorney inside the department said of the new AG. “He’s spent so much time trying to suck up to the president to get here. But this is a big job. It comes with many responsibilities. He just simply doesn’t have the wherewithal.”

Whitaker’s ascension to the rank of top law enforcement officer in the country has been as swift as it's been controversial. A former U.S. attorney-turned-conservative media pundit, he served for months as former AG Jeff Sessions’ chief of staff before being appointed to fill his old boss’s post. That résumé hasn’t instilled confidence.

“We’ve seen this over and over again with the Trump administration. They never vet these people,” said one former official from the department. “It shows that they don’t really have a strategy when it comes to these things and then they end up having to backtrack.”

But there are some in the department who are willing to give him a chance. One attorney who knew and worked with Whitaker said that when he entered his job as U.S. attorney for the southern district of Iowa in 2004, he faced a “steep learning curve.” But another attorney who encountered Whitaker said he was “humble enough to recognize that he didn’t know everything.”

“When I first encountered Matt I thought he was a bright guy who struck me as someone packaged in a very sort of good old farm boy football player package,” one of the attorneys said. “He was not a know-it-all. He asked a lot of questions. He really wanted to carry out the job effectively.”

But Whitaker is no longer occupying a post where he has time to learn and adjust. He now is running a department with more than 100,000 employees, a budget of roughly $30 billion, and with oversight of and input into every federal law enforcement matter in the country. Already, Whitaker has signed off on a controversial new regulation that will allow President Trump to prohibit certain immigrants from seeking asylum. The department is currently prepping for December hearings in the AT&T-Time Warner case, in which DoJ has appealed the $85 billion merger. It is also also knee-deep in its lawsuit to block California’s new net neutrality law from going into place.

“ We’ve seen this over and over again with the Trump administration. They never vet these people. It shows that they don’t really have a strategy when it comes to these things and then they end up having to backtrack. ” — A former official from the department.

Kerri Kupec, acting principal deputy director at the DoJ, defended Whitaker from his critics, saying that he is a "respected former U.S. Attorney and well-regarded at the Department of Justice. As Deputy Attorney General Rod Rosenstein said today, he is a superb choice.”

But the vast powers that Whitaker has not been given have left officials and trial attorneys at DoJ fearful that, in an effort to impress President Trump, he will try to make up for his inexperience by making rash decisions about the direction of the department, including implementing policy changes in the Division of Civil Rights.

“This guy has spent his whole life trying to climb the rungs of power to get to a federal appointment,” one DOJ official said. “Now that he is here, and who knows for how long, he’s going to try and make a name for himself. And that could make things harder for us.”

Originally from Iowa, Whitaker started his career as an attorney in Des Moines before running unsuccessfully for state treasurer in 2002. In 2004, President George W. Bush appointed him as the U.S. attorney. After leaving that office in 2009, he sought to build up his political connections, often meeting with influential lawmakers and think-tank leaders, two individuals who worked alongside him in the Department of Justice said.

Whitaker headed Minnesota Gov. Tim Pawlenty’s presidential campaign in Iowa in 2012 before moving on to work in a similar capacity for Texas Gov. Rick Perry during his short-lived bid that same year. In 2014, he ran for a U.S. Senate seat in Iowa but lost in the GOP primary to eventual winner Joni Ernst. That same year, he worked as chairman for then-Republican candidate for State Treasurer Sam Clovis. Clovis, a former Trump campaign official, has been questioned by the Special Counsel’s office.

During the first year of the Trump presidency, Whitaker shuttled back and forth between Washington, D.C. and New York, making numerous media appearances in an attempt to catch the president’s attention. In those appearances, Whitaker blasted the Mueller investigation, claiming there was “no collusion” between the Russians and the Trump campaign.

It worked. Though there are constitutional questions surrounding the appointing, Whitaker was named acting AG this Wednesday after Sessions’ forced resignation. On Friday, President Trump claimed he did not know Whitaker. But three people inside DOJ said that after stepping into his role of DoJ chief of staff in September 2017, Whitaker frequented the White House with Sessions and developed a working relationship with the president and his advisers.

It’s not just Whitaker’s efforts to appease the president that have people inside the Department of Justice on edge. His past business dealings and connection to FACT, a partisan watchdog group, have raised concerns that, as attorney general, he will make rash decisions about how to revamp department policies, including those that deal with immigration, criminal justice reform, gun rights, and antitrust.

Inside DOJ, Whitaker’s political views are known to be similar to Sessions’. But officials there said that his unpredictability, and lack of institutional experience, could lead the department in a more conservative direction. Whitaker has written several opinion pieces in the national media and spoken publicly about about his conservative take on the law.

“I have a Christian worldview,” Whitaker said in a 2014 interview while campaigning in Iowa. “Our rights come from our Creator and they are guaranteed by the Constitution.”

Whitaker has also said he thought Marbury vs. Madison—a landmark decision that gives courts the power to declare legislative and executive acts unconstitutional—was a “bad ruling.” It’s those comments that have trial attorneys inside the civil rights division of the Department of Justice worried.

“The civil rights division is always more political than the other divisions,” said one trial attorney. “But the feeling is this guy is going to come in and take a tougher stance on policy matters like immigration.”

A previous version of this story said that a spokesperson at DoJ did not comment. The reason they did not, however, was because of a technological mishap. Their comment has since been added to the story.