The peak year for Apollo appropriates was 1967. LBJ began the cuts because he needed money for his "guns and butter" programs - the Vietnam War and his Great Society programs.

Nixon continued the cuts that LBJ started. It helps to remember that Nixon had a solidly Democrat controlled Congress throughout his administration. Many members of Congress had tried to cut the Apollo budget long before Apollo 11. Once JFK's goal was met and public interest faded (by Apollo 13, people were complaining about their soap operas being preempted by space coverage), there was little political will to continue NASA funding.

During the 1970s and following the Apollo missions, the only significant American space events were Skylab, Apollo-Soyuz, and Viking. Following the Apollo-Soyuz mission, there were no manned flights for years as the Shuttle dragged through development. Virtually nothing significant happened through Carter's administration.

It was Reagan that proposed a permanent space station. It was supposed to be flying by 1990 at an estimated cost of somewhere around $8-12 billion (not counting operations). Congress, especially in the late 1980s when the Democrats had the majority, did keep the program alive on a shoestring. Redesign followed redesign and the cost spiraled through the mid 1990s.