“There is a definite difference in the mentality of the Department of Justice, and you see it already,” said Mr. Tolman, who previously worked as counsel to Senator Orrin G. Hatch, Republican of Utah. Mr. Tolman praised past bipartisan progress on criminal justice reform and said Mr. Sessions was out of step: “This is the 1980s and ’90s mentality, and an absolute 180-degree reversal from what we’ve learned.”

Mr. Sessions has not loudly promoted the changes. In travels around the country, he has rarely spoken with the press as public attention has centered on the government’s Russia inquiry. Mr. Sessions recused himself from the investigation in March after his own undisclosed meetings with the Russian ambassador became public. He left in charge Mr. Rosenstein, who in turn appointed Mr. Mueller, a former F.B.I. director, as special counsel.

Mr. Sessions’s recusal has gnawed at the president, who has said he would have chosen a different attorney general had he known Mr. Sessions would step away from the inquiry — something Mr. Sessions did in keeping with the guidance of the Justice Department’s ethics lawyers. Mr. Trump, who considered Mr. Sessions a loyalist, has called the recusal “unfair to the president” and chastised Mr. Rosenstein for appointing Mr. Mueller.

Even as Mr. Trump’s new chief of staff, John F. Kelly, assured Mr. Sessions this week that he was not at risk of being fired, Mr. Trump has issued no such reassurance.

Beyond personal attacks, the president has taken broader swipes at the department for how it has defended his travel ban, which aimed to close the nation’s borders to travelers from certain predominantly Muslim countries. He has also called for criminal inquiries into Hillary Clinton while calling the Russia investigation a “witch hunt.”

The tension between the Justice Department’s leadership and the president, however, has made some career prosecutors and senior officials — including supporters of the administration’s agenda — uneasy, according to more than two dozen current and former Justice Department officials.

Since May, Mr. Rosenstein has addressed an array of Justice Department staff members, from the public integrity section in Washington to field offices of federal prosecutors in Nevada and South Carolina, seeking to deliver a simple message: Business as usual.