President Eisenhower was asked if there should be a military parade to show off its might.....

[highplainsdem]

17. The term "third rail" for Social Security started with a Tip O''Neill aide in 1982, according to Wikipedia. But

Eisenhower did warn about the political stupidity of any political party touching it, most famously in a widely quoted 1954 letter to his brother.

Wikipedia: https://en.wikipedia.org/wiki/Third_rail_(politics)

That Eisenhower letter:

https://teachingamericanhistory.org/document/letter-to-edgar-newton-eisenhower/

Now it is true that I believe this country is following a dangerous trend when it permits too great a degree of centralization of governmental functions. I oppose this–in some instances the fight is a rather desperate one. But to attain any success it is quite clear that the Federal government cannot avoid or escape responsibilities which the mass of the people firmly believe should be undertaken by it. The political processes of our country are such that if a rule of reason is not applied in this effort, we will lose everything–even to a possible and drastic change in the Constitution. This is what I mean by my constant insistence upon “moderation” in government. Should any political party attempt to abolish social security, unemployment insurance, and eliminate labor laws and farm programs, you would not hear of that party again in our political history. There is a tiny splinter group, of course, that believes you can do these things. Among them are H. L. Hunt (you possibly know his background), a few other Texas oil millionaires, and an occasional politician or business man from other areas. Their number is negligible and they are stupid.

The last four sentences there - starting with "Should any political party..." - are the most widely quoted.