 He served as Deputy Director for Operations from January 11, 1978, to April 12, 1981, and later, nominated by US President Ronald Reagan, as Deputy Director of Central Intelligence under Director William J. Casey as of April 27, 1982, succeeding Bobby Ray Inman.Questioning McMahon during his nomination included US Senators Daniel Patrick Moynihan (who guided publication of the VENONA papers in the mid-1990s.In March 4, 1986, McMahon, age 56, resigned and left office on March 26, succeeded by Robert M. Gates.