Justice Department veterans generally heaved ecstatic sighs of relief after Donald Trump announced last week that William Barr, who served as attorney general under George H.W. Bush, would return for a second stretch as America’s top lawyer. After all, acting attorney general Matthew Whitaker remains something of an unknown quantity—a power-lifting former tight end perhaps best known for his scathing evaluation of Robert Mueller’s investigation. “My reaction is one of relief for the institution of the Department of Justice and the F.B.I.,” said David Laufman, a former Justice Department official who oversaw the Hillary Clinton e-mail and Russia probes. “What the department and the bureau need most now is an experienced, respected, steady hand who demonstrably has both the intellect and the commitment to these institutions and the rule of law to provide the type of leadership that they and the country deserve.”

But Barr, too, has his own history. He’s offered controversial statements about the Mueller investigation; argued that the Uranium One scandal warrants greater investigation than the Trump campaign’s Russia ties; questioned the ideological bent of Mueller’s team; and defended the president’s decision to fire former F.B.I. Director James Comey. Lawyers I spoke with stopped short of classifying Barr’s remarks as disqualifying, but they did note they’ll be placed under a microscope. “They may not be red flags, but they’re certainly factors that the Senate Judiciary Committee should take into account in posing questions to him at his confirmation hearing to give him an opportunity to explain what he meant and to assess whether he brings any preconceived notions or biases to the job that potentially would be grounds for recusal,” Laufman said.

Indeed, Mueller’s fate is still murky. Even if Barr leaves his probe untouched, the Senate is not expected to take a confirmation vote on his nomination until early next year, leaving Whitaker in charge for at least the coming weeks. At this point, however, even the most hell-bent A.G. may find it difficult to smother the special counsel’s probe. “I think the train has left the station,” Harry Litman, a former United States attorney and deputy assistant attorney general, told me, citing last week’s court filings related to Michael Cohen, Paul Manafort, and Mike Flynn. The filings, he said, “include chapter and verse about evidence—most of which you don’t see—but it’s now in a repository in the court, so in that sense, it can’t come back in the bottle. Whitaker or Barr or whatever couldn’t suck it back in. It’s now in the province of the court.”

Notably, perhaps the most damning revelation across the filings for the president came from the Southern District of New York—not Mueller. In its sentencing memo, S.D.N.Y. alleged that Cohen committed campaign finance violations in coordination with, and at the direction of, Donald Trump when he facilitated hush payments to Stormy Daniels and Karen McDougal. “I think it’s too late to pretend that didn’t happen,” Litman added. In a closed-door testimony before the House Judiciary Committee last week, Comey made a similar argument. “You’d almost have to fire everyone in the F.B.I. and the Justice Department to derail the relevant investigations,” he said when asked what effect a Mueller firing would have on the Trump-Russia investigation.

Of course, that doesn’t mean Mueller is out of the woods. “I don’t think the Mueller probe is insulated,” Elliot Williams, the former deputy assistant attorney general for legislative affairs at D.O.J., told me. “Certainly between the Southern District of New York—and perhaps other prosecutors and law offices around the country, investigative work has been spread or shared outside of just the special counsel’s office.” But, he continued, “that doesn’t mean that the White House, and perhaps even the Justice Department, could not act to tamper or conceal or meddle with the due administration of justice in the form of the investigation.”

What seems unquestionable, however, is that Barr is in for a real headache, situated between a shrill and defensive president and an indefatigable special counsel. (“It’s likely to be a really turbulent time in the history of the Department of Justice.” Timothy Flanigan, who served under Barr as assistant attorney general in charge of the Office of Legal Counsel, told me.) So why would a former A.G., who has made a small fortune in the private sector, want to take a job that practically broke even Trump loyalist Jeff Sessions? It’s an open question among those on the D.C. bar. “Who would take this job? What attorney would want the job of attorney general under this president?” Williams asked incredulously. “Even someone who has been an attorney general before—who understands the job and understands the role—runs the risk of being put in an incredibly compromising or career-damaging position by being associated with this president, who does not regard the attorney general role as independent.”

Flanigan suggested Barr could be driven by a sense of duty. “He probably understands that the department severely needs someone with great credibility and to help kind of restore morale, to restore public perception of the department, and I believe he felt kind of called upon to do that,” he told me. “If you subtract self-interest, what you’re left with is either randomness or selflessness.”

Barr, who is 68, may also feel that he is unintimidated by Trump. And while some I spoke with disagreed with Barr’s politics—one Washington attorney described him as a “staunch Catholic conservative”—he is widely viewed as an institutionalist steeped in Justice Department tradition. He also may be able to take the pressure that crippled Sessions. “If it ever came to the president pushing back on Bill or pushing on Bill, he’s going to find that Bill has the capability to push back,” Flanigan told me. “He’s got all the money he needs. He’s got an amazing career behind him. I don’t think he’s going to just say, ‘Yes, sir, Mr. President. I’m sorry, sir.’ I think he’s going to have the strength of his convictions.” He continued: “I don’t think he’d be a shrinking violet.”