Around that time, Mr. Trump also reached out to Mr. Comey, despite guidance from Mr. McGahn that the president should avoid talking directly to Justice Department officials. “The president asked Comey to ‘lift the cloud’ of the Russia investigation” by saying publicly that he was not under investigation, the report said. Mr. Comey refused.

May 9, 2017

Firing Comey

Mr. Trump struggled to get Mr. Comey to say publicly that he was not under investigation. Those frustrations finally came to a head in May 2017 when the president decided Mr. Comey needed to be fired.

The president first said he fired Mr. Comey because of how he handled the investigation into Ms. Clinton’s emails, but he soon strayed from that explanation. Within days, Mr. Trump appeared to say in an NBC News interview that Russia was on his mind when he dismissed Mr. Comey; at another point, he told senior Russian officials in the Oval Office that, by firing Mr. Comey, he had relieved great pressure on himself.

The report said that even though the White House relied on so-called independent recommendations for the dismissal from Mr. Sessions and deputy attorney general, Rod J. Rosenstein, Mr. Trump had decided to fire Mr. Comey regardless of what they said. “The day after firing Comey, the president told Russian officials that he had ‘faced great pressure because of Russia,’ which had been ‘taken off’ by Comey’s firing,” the report said.

June 17, 2017

Reacting to the Mueller appointment and trying to fire him

After learning in May 2017 that Mr. Mueller had been appointed, Mr. Trump told advisers that it was “the end of my presidency” and demanded Mr. Sessions resign. Mr. Sessions submitted a resignation letter to Mr. Trump, who began carrying it around and asked advisers what he should do with it.

In the weeks after Mr. Mueller began his work, Mr. Trump tried to force Mr. McGahn to have the Justice Department fire Mr. Mueller, citing what the president perceived as conflicts of interest. Mr. McGahn thought the president’s assertions carried little weight and refused to follow his instructions, he has told investigators.

On Saturday, June 17, 2017, Mr. McGahn said, the president called him at home and insisted he have Mr. Mueller fired. Fed up with the repeated directive, Mr. McGahn drove to the White House, packed up his office and told senior White House officials that he planned to quit. They advised Mr. McGahn to ignore Mr. Trump, and the lawyer remained in his post another year.