Robert Mueller Returns to Political Fire After Long Career With FBI

WASHINGTON—Robert Mueller’s appointment as special counsel in the Russia probe brings the 72-year-old former Federal Bureau of Investigation director back into the political fire, a place where he has long managed to survive and thrive with his credibility largely unscathed.

Mr. Mueller ran the FBI from 2001 to 2013, reshaping the bureau to focus on counterterrorism after the Sept. 11 attacks, which confronted him a week into the job…