To many who have followed the career of Deputy Attorney General Rod J. Rosenstein, the longtime prosecutor’s starring role in drama surrounding the ouster of FBI Director James B. Comey has left them surprised — and a little bit baffled.

Rosenstein, who took office last month, has been spared much of the criticism being aimed at President Trump and his top lieutenants. But Rosenstein’s authorship of the memo that was used as a justification for Comey’s firing has prompted some to wonder whether the Justice Department’s No. 2 was fully committed to firing the FBI director — or whether he was drawn into a White House plan to thwart the FBI’s investigation of potential ties between the Trump campaign and Russia.

Some associates took to parsing the words of the memo, which did not directly call for Comey to be fired but said that the FBI “is unlikely to regain public and congressional trust until it has a Director who understands the gravity of the mistakes and pledges never to repeat them.”

“He didn’t say, ‘I recommend firing Comey,’ ” said Eric Columbus, who was a senior adviser to the deputy attorney general under President Barack Obama. But “I’m guessing that Rosenstein wanted to push back as much as he could without getting fired.”

Others cautioned against tying Rosenstein’s views to those of Trump’s.

(Jenny Starrs,Julio Negron/The Washington Post)

“The problem here for Rod is people are ascribing the president’s motives to him, and they’re acting out of entirely differently motivations,” said Tim Maloney, a longtime Maryland defense lawyer who has worked with Rosenstein.

“Rod cares deeply about the integrity of the criminal justice system. These are very different motivations leading to the same result,” he said.

Maloney said Rosenstein was apolitical and was “not going to think about what is the best place or time on the public calendar to get rid of the FBI director. He’s going to look at the merits.”

Rosenstein, 52, was named by President George W. Bush to be U.S. attorney in Maryland and reappointed by Obama, and he has won praise from lawmakers in both parties as a straight-

arrow prosecutor.

Rosenstein served on the Whitewater prosecution team that investigated Bill and Hillary Clinton’s real estate dealings in the 1990s, and his office took down Prince George’s County Executive Jack B. Johnson on bribery and corruption charges.

Rosenstein, who declined to comment, lives in Bethesda with his wife, a former assistant U.S. attorney, and their two teenage daughters.

From the moment he took office as the Justice Department’s No. 2, Rosenstein’s role has taken on special meaning in the context of the FBI’s investigation into possible ties between Trump’s campaign and Russia. Because Attorney General Jeff Sessions recused himself from the inquiry, Rosenstein is effectively in charge of a case with deep political and legal implications for the president and his associates. Rosenstein, for instance, also has the authority to appoint a special counsel.

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His participation in the Comey ouster took shape this week after he and Sessions attended a previously scheduled lunch with Trump on Monday.

The president wanted to get rid of Comey. After the Justice Department officials laid out their view, Trump asked them to put their thoughts in writing, and Rosenstein on Tuesday wrote his memo, according to White House officials.

Rosenstein threatened to resign after the narrative emerging from the White House on Tuesday evening cast him as a prime mover of the decision to fire Comey and that the president acted only on his recommendation, according to a person close to the White House, who spoke on the condition of anonymity because of the sensitivity of the matter. Justice Department officials declined to comment on the claim.

The White House released the three-page letter as it announced the firing Tuesday.

Columbus and others noted that Rosenstein said in his memo that he agreed with former Justice Department officials who had criticized Comey. However, while all of those former officials were critical of Comey’s actions in the investigation of Hillary Clinton’s emails, none recommended that he be fired. Moreover, at least two of those former officials, Donald Ayer and Alberto Gonzales, criticized Trump’s decision to fire Comey. Ayer said the firing was a “sham,” and Gonzales said the president failed to make the case for it, leaving people to “assume the worst.”

Several of Rosenstein’s former colleagues cited what they called a crucial distinction in the memo. They said there is a difference between believing that Comey mishandled matters such as the Clinton email investigation and the idea that the person overseeing an investigation into whether Russia aided Trump’s campaign should be fired by Trump. It is the latter that created much of the controversy over Trump’s decision.

Rosenstein’s memo partly relied on news accounts and statements by Democrats to accuse Comey of overstepping his authority in the Clinton case.

Comey in July announced that the FBI would not recommend criminal charges against Clinton in the email case but said she was “extremely careless in handling classified material.”

Then, in October, he announced that the FBI was reopening the investigation, which Clinton has said cost her the election. Comey testified May 3 that reopening the investigation was justified because a Clinton aide forwarded “hundreds and thousands of emails” to her husband, but the Justice Department said Tuesday that Comey misspoke about the number.

Some who have worked with Rosenstein worried Wednesday that the deputy attorney general had, by laying out widely held criticisms of Comey’s handling of the Clinton email investigation, provided Trump the political cover he needed to remove Comey just as the Russia probe appeared to be heating up.

Paul Butler, who worked with Rosenstein in the public integrity section of the Justice Department, said that prosecutors who come through that unit are trained to be apolitical. The public integrity section was created in response to Watergate, with prosecutors going after FBI agents, Democrats, Republicans and others to combat the social ills of public corruption.

“One of the ways you fight public corruption is to follow the rules,” said Butler, now a professor at Georgetown Law. “What ­[Comey] did in July and October with those remarks about Secretary Clinton broke all the rules. That is exactly what Rosenstein said in the memo.”

Butler said that even if Rosenstein were aware of possible political motivations the president had for ousting Comey, it would not stop someone who came up through the public integrity unit from rendering an opinion as Rosenstein did.

“Might he have known when he was giving the president his opinion that Comey was unfit to serve that the president could use that to his political advantage?” Butler asked. “He could have, but should that have stopped him from rendering his honestly held and carefully considered point of view? No.”

Robert Bonsib, a former assistant U.S. attorney and now a Maryland defense lawyer, said the memo was not surprising.

“If somebody in Rod’s office when he was U.S. attorney stepped out and made those kinds of statements about an ongoing investigation, Rod would have fired that person, as well,” Bonsib said.

Bonsib called the memo a “very professional, nonpolitical document” and said it would have been unremarkable except for the fact that Comey was investigating connections between Trump and Russia.

Rosenstein’s former colleagues said Comey’s dismissal played out in ways that were both typical and atypical of Rosenstein’s style.

It was typical in that the memo was grounded in the rule of law and focused on protecting the institutional interests of the Justice Department. But it was atypical in that Rosenstein — a graduate of the Wharton School who is known to give books about management to new supervisors — would not have fired someone so abruptly that they had to hear of their ouster from the media.

Trump’s nomination of Rosenstein to be the nation’s second-ranking law enforcement official drew bipartisan praise, and he was confirmed by a 94-to-6 vote on April 25.

Rosenstein said in a written response to questions from Sen. Patrick J. Leahy (D-Vt.) during his confirmation hearing that he was not prepared to say whether a special prosecutor should be appointed in the Russia investigation, but he promised to study the matter and make an independent decision. In the wake of Comey’s firing, calls for a special prosecutor have escalated, but Rosenstein has not offered his view.

Leahy said Wednesday that the chain of events leading to Comey’s firing underscores that “a special counsel must be appointed to lead the Russia investigation. The American people must have confidence that ours is a government of laws, not of Donald Trump’s whims.”

Matt Zapotosky and Sari Horwitz contributed to this report.