Clark, who Time magazine in 1983 named as "the second most powerful man in the White House,” began working for Reagan in 1966 by managing the then-actor's gubernatorial campaign in California.

After Reagan won the governorship, Clark served as his executive secretary in Sacramento. Reagan later appointed Clark to the state appellate court in Los Angeles and then the state Supreme Court.

Clark moved with Reagan to the White House to serve as deputy secretary of State, national security adviser and finally Interior secretary. Clark was a key player in Reagan's dealings with the Soviet Union.

Clark is survived by five children.

β€œIt's been a hard fight for him, but we do feel he's in a better place and he's not suffering any longer,” Paul Clark, his son, said.