Here, Mr. Rosenstein shifts to complaints, heard largely from Democrats, about Mr. Comey’s highly unusual news conference.

It portrays Mr. Comey’s late-October letter as a mistake.

“Concerning his letter to the Congress on October 28, 2016, the Director cast his decision as a choice between whether he would ‘speak’ about the decision to investigate the newly-discovered email messages or ‘conceal’ it. ‘Conceal’ is a loaded term that misstates the issue. When federal agents and prosecutors quietly open a criminal investigation, we are not concealing anything; we are simply following the longstanding policy that we refrain from publicizing non-public information. In that context, silence is not concealment.”

This is a rebuttal to Mr. Comey’s testimony at a congressional hearing last week, when he defended his decision to send a letter to Congress about newly discovered emails (which turned out to be immaterial) 10 days before the presidential election. Faced with the same circumstances, Mr. Comey said he would do it all over again. Mr. Comey’s letter, which quickly became public, cast a negative cloud over Mrs. Clinton in the closing days of the election, and her lead in the polls over Mr. Trump dwindled.

It frames dissatisfaction with Comey in bipartisan terms.

“My perspective on these issues is shared by former Attorneys General and Deputy Attorneys General from different eras and both political parties.”

In this section, Mr. Rosenstein emphasizes that his recommendation is not driven by partisan considerations, but rather by his break from Justice Department traditions and procedures. To that end, he quotes at length from a series of top former Justice Department officials from both parties who publicly criticized Mr. Comey’s handling of the email investigation at least partly in those terms. They included two Democrats: former Attorney General Eric H. Holder Jr. of the Obama administration and Jamie S. Gorelick, a deputy attorney general during the Clinton administration.

It says Comey’s exit is necessary if the F.B.I. is to heal.

“The way the Director handled the conclusion of the email investigation was wrong. As a result, the F.B.I. 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. Having refused to admit his errors, the Director cannot be expected to implement the necessary corrective actions.”

The attention will now turn to whom Mr. Trump nominates to succeed Mr. Comey in overseeing the F.B.I. — and the investigation into the contacts between Russia and Trump associates.