Matthew Whitaker, whom President Donald Trump named as his acting attorney general on Wednesday, privately provided advice to the president last year on how the White House might be able to pressure the Justice Department to investigate the president’s political adversaries, Vox has learned.

Whitaker was an outspoken critic of special counsel Robert Mueller’s probe before he became the chief of staff to Attorney General Jeff Sessions in September 2017. That has rightfully raised concerns that Whitaker might now attempt to sabotage Mueller’s investigation. But new information suggests that Whitaker — while working for Sessions — advocated on behalf of, and attempted to facilitate, Trump’s desire to exploit the Justice Department and FBI to investigate the president’s enemies.

Whitaker’s open sympathizing with Trump’s frequent complaints about the Mueller investigation resulted in an unusually close relationship between a president and a staffer of his level. The president met with Whitaker in the White House, often in the Oval Office, at least 10 times, a former senior administration official told me. On most of those occasions, Sessions was also present, but it’s unclear if that was always the case.

During this period, Whitaker frequently spoke by phone with both Trump and Chief of Staff John Kelly, this same official told me. On many of those phone calls, nobody else was on the phone except for the president and Whitaker, or only Kelly and Whitaker. As one senior law enforcement official told me, “Nobody else knew what was said on those calls except what Whitaker decided to tell others, and if he did, whether he was telling the truth. Who ever heard of a president barely speaking to his attorney general but on the phone constantly with a staff-level person?”