 After Johnson became president in November 1963 following Kennedy's assassination, Clifford served frequently as an unofficial White House Counsel and sometimes undertook short-term official duties, including a trip with General Maxwell Taylor in 1967 to South Vietnam and other countries in Southeast Asia and the Pacific.On January 19, 1968, Johnson announced his selection of Clifford to succeed Robert McNamara as the U.S. Secretary of Defense.Clifford estimated that, in the year just prior to his appointment, he had spent about half of his time advising the President and the other half working for his law firm.