The Evolution of programs and policies for civil defense was written by B. Wayne Blanchard, Ph.D., Planning Specialist for Civil Defense Programs Federal Emergency Management Agency 1985.
This is the link to that document. It is a short PDF and well worth the time to read and understand how the various presidential administrations either supported or de-emphasized the program. Let me know what you think.
https://training.fema.gov/hiedu/docs/blanchard%20-%20american%20civil%20defense%201945-1984.pdf