Robert Mueller, the former FBI director and special counsel leading the Russia investigation, leaves the Capitol in Washington.

FILE — Robert Mueller, the former FBI director and special counsel leading the Russia investigation, leaves the Capitol in Washington, June 21, 2017. Mueller has issued subpoenas from a Washington-based grand jury in recent weeks, according to several lawyers involved in the case, the New York Times reported on Aug. 3. (Doug Mills/The New York Times)