If the firing of former FBI director James Comey is part of a Trump administration plot to foil the investigation into Russian election meddling—as many of the president’s opponents have alleged—Deputy Attorney General Rod Rosenstein is an odd conspirator. In a three-page memo reportedly pivotal to President Trump’s decision, Rosenstein wrote that the director had to go if the agency hoped to “regain public and congressional trust.” Those are damning words from a man whose integrity has been compared to that of Jimmy Stewart, the actor who portrayed egoless small-town heroes driven by bygone ideals: of right and wrong, and black and white in a world gone increasing gray.

Just last week, Rosenstein was relatively unknown to the American public. And only the week before that had he been appointed to the position of deputy attorney general, a role that put him at the head of the investigation into alleged connections between the Trump administration and Russia. His confirmation late last month, although part of a contentious transition, came with wide bipartisan support. He has served under five presidents, and he was one of only three U.S. attorneys—out of 93 nationwide—asked to stay on when the White House switched hands from George W. Bush to Barack Obama. He is meek in appearance and mild in tone. In his prior office as U.S. attorney for Maryland, beside a photo of his family, he kept a plaque on the wall that read: “Don’t tell me what I want to hear. Just tell me what I need to know.”

No frills. Apolitical. The “poster child for the professional, competent, ethical, and fair-minded prosecutor” is one way Rosenstein has been described. Now he finds himself in an unfamiliar position, and in an administration lavished in controversy.

Before he left his position in Maryland, Rosenstein reflected on his 12 years as the most powerful prosecutor in the state in an interview with The Baltimore Sun. He had just been voted into office, and as he readied to move to Washington, D.C., he said he hoped to continue doing his “job without regard to partisan political consideration.”And for decades that seemed his primary task. He grew up in Philadelphia and graduated from the Wharton School at the University of Pennsylvania (where Trump also studied). He earned a law degree from Harvard in 1989, then took a job in the DOJ’s public-integrity section.

In the mid-1990s Rosenstein was recruited to a team of prosecutors that handled the Whitewater Development Corporation investigation, the case that looked into Bill and Hillary Clinton’s business dealings with an associate. In what was a highly politicized, highly partisan investigation, Rosenstein came out in exemplary form. “I would have trusted him with anything,”  Philip B. Heymann, who was deputy attorney general in the Clinton administration told The Washington Post in 2011. “If there was a case where I was worried there was a perception we were being unfair, I would trust him to do the right thing and to do the job.”

In 2005 Rosenstein became the top federal prosecutor in Maryland, and one of his most memorable cases was that of Jack B. Johnson, county executive for Prince George’s County. Johnson was accused of taking more than a million in bribes, extorting witnesses, and evidence tampering. The case against him was credited with being so tight that Johnson and 14 others pleaded guilty before it went to trial. Soon, the Bush administration transitioned to the Obama administration, and Rosenstein was kept on.

When Trump came to the White House, he was the only remaining holdover from the Bush era. In the interview with the Sun, Rosenstein said that as Trump took office he got calls from attorneys all over the country asking how they might keep their jobs. “Here’s what I did,” Rosenstein told the Sun about his advice, “I sat in my office and did my job, and I’m grateful someone made the decision to keep me here.”

Unlike his boss, Attorney General Jeff Sessions, Rosenstein did not campaign with Trump or offer any kind of high-profile support. But his straight-arrow reputation may have been a useful tool for the administration.

In one alternative theory to that proffered by some Democrats—in which Trump’s decision to fire Comey grew out of a fear that the FBI was increasingly prying into his office’s links with Russia—there’s a different sort of timeline. Byron York wrote in the Washington Examiner that perhaps Trump had always planned to fire Comey, but was just waiting for Rosenstein to make it happen.

York wrote that some in the Trump camp wanted Comey gone immediately—as in, January 20. But those who wanted to maintain the appearance of protocol needed to wait: first for the confirmation of Jeff Sessions, which was being held up, and later for Rosenstein’s. After that, the administration could potentially count on Rosenstein to give Comey’s dismissal more legitimacy.

But opposition to Sessions was fouling this plan up, York writes:

First, it took a long time to get an attorney general in office. Facing Democratic opposition, Jeff Sessions, one of the president’s first nominees, was not confirmed by the Senate until Feb. 8. Then, it took a long time to get a deputy attorney general in place. Rod Rosenstein, the deputy—and the man who wrote the rationale for axing Comey—faced similar Democratic delays and was not sworn in until April 26.

This theory seems like it could account for some of the dissonance between Trump’s posture and Rosenstein’s memo. In his account, Rosenstein found fault in the way Comey acted during the Clinton email investigation, not because the FBI didn’t bring charges against her, but because Comey had irreparably politicized his agency. Yet Trump had previously expressed support for Comey’s actions with regard to Clinton.

“Over the past year,” Rosenstein wrote, “the FBI’s reputation and credibility have suffered substantial damage, and it has affected the entire Department of Justice. … I cannot defend the director’s handling of the conclusion of the investigation of Secretary Clinton’s emails, and I do not understand his refusal to accept the nearly universal judgment that he was mistaken. Almost everyone agrees that the director made serious mistakes; it is one of the few issues that unites people of diverse perspectives.”

Rosenstein has only been in office for two weeks—about as long, some reports say, that Trump had been asking his staff to look for reasons to fire Comey. So when squeaky-clean Rosenstein filed his report, York says, it offered the perfect excuse. It didn’t matter that Rosenstein’s case against Comey didn’t match the president’s own alleged reasons for wanting to fire him. To support his theory of the alternate timeline, York references an interview Trump gave with Fox Business in April.

“Was it a mistake not to ask Jim Comey to step down from the FBI at the outset of your presidency?” Maria Bartiromo asked. “Is it too late now to ask him to step down?"

“No, it’s not too late,” Trump said. Then he added, “it’s going to be interesting.”

Rosenstein has probably barely had time to put the plaques on the wall from his past office, and already he’s found himself in a position he spent decades trying to avoid. That hed long been widely respected by both Democrats and Republicans seems unquestionable. But in this hyperpartisan atmosphere, and in an administration that relishes controversy, how long can that reputation last?