Mr. McGahn was a witness to many episodes described in the second volume of the Mueller report, which centered on potential obstruction of justice issues; his name appears there more than 500 times.
In June 2017, for example, Mr. Trump called Mr. McGahn at home and ordered him to tell Rod Rosenstein, the deputy attorney general, to fire Mr. Mueller over a dubious claim that the special counsel had a conflict of interest. Mr. McGahn refused and was prepared to resign before Mr. Trump backed off, according to the Mueller report.
After the report became public, Mr. Trump claimed on Twitter that he had never told Mr. McGahn to fire Mr. Mueller. Two people familiar with the hearing on Friday said that the session had spent a lengthy period going over that episode, and that Mr. McGahn had testified under oath that the account in Mr. Mueller’s report was accurate.
The report also described a related episode that followed a January 2018 report by The New York Times that first brought to public light Mr. Trump’s failed attempt to have Mr. Mueller fired. Mr. Trump tried to bully Mr. McGahn into creating “a record stating he had not been ordered to have the special counsel removed” while also shaming the lawyer for taking notes about their conversations. But Mr. McGahn refused to write the memo.
Mr. McGahn was also a major witness to several other episodes recounted in the obstruction volume of Mr. Mueller’s report, including the White House’s handling of the Justice Department’s concerns that Mr. Trump’s first national security adviser, Michael T. Flynn, was vulnerable to blackmail by Russia over false statements he had made about his conversations with the country’s ambassador. Mr. McGahn was also part of deliberations leading to Mr. Trump’s firing of James B. Comey Jr., the F.B.I. director.
Mr. Trump had directed Mr. McGahn to speak with Mr. Mueller’s investigators in 2017. In 2019, as it became clear that Mr. McGahn had become a chief witness to many of Mr. Trump’s actions that raised obstruction of justice concerns, the president’s allies — like his personal lawyer Rudy Giuliani — began attacking him.
The attacks left Mr. McGahn in a delicate position. He is a hero to the conservative legal movement because he was the chief architect of the Trump administration’s judicial selection process, which filled the federal bench with Federalist Society-style appointees. But Mr. McGahn’s law firm, Jones Day, has many Republican-oriented clients; if Mr. Trump were to order the party faithful to shun the firm as punishment, it could be financially devastating.