Associated Press/Alex BrandonReince Priebus, the former White House chief of staff sat down with special counsel Robert Mueller on Friday as part of the ongoing investigation of Russia's meddling in the US election, according to Preibus' attorney, William Burck, who was cited by Politico. Priebus, who left the Trump administration in July, had previously said he would cooperate with the investigation, and a statement from Burck reaffirmed that on Friday: “Mr.