In the 1970s, I never heard a single claim that Nixon had immunity.
except one:
“During David Frost’s series of interviews with Richard Nixon, Nixon (in)famously said
‘when the President does it, that means that it is not illegal, by definition.’”
reader comment:
The context, clearly indicated in your quote, is the Huston Plan, which involved mass surveillance of US citizens, burglary, and even potentially internment camps for “radicals.” It was an assertion that any crime could be committed if it was claimed to be in the national interest (preventing people from making the nation less “peaceful” and “orderly”).
Nixon:
Well, what I, at root I had in mind I think was perhaps much better stated by Lincoln during the War between the States. Lincoln said, and I think I can remember the quote almost exactly, he said, “Actions which otherwise would be unconstitutional, could become lawful if undertaken for the purpose of preserving the Constitution and the Nation.”
link given above:
https://politics.stackexchange.com/questions/78917/was-nixons-when-the-president-does-it-that-means-that-it-is-not-illegal-tech
You must have never heard of United States v. Nixon, 418 U.S. 683 (1974), in which the Supreme Court held that the President does not have "an absolute, unqualified Presidential privilege of immunity from judicial process under all circumstances." In that case, the issue was merely whether the President can ignore all judicial subpoenas. The Supreme Court found that "Absent a claim of need to protect military, diplomatic, or sensitive national security secrets, the confidentiality of Presidential communications is not significantly diminished by producing material for a criminal trial under the protected conditions of in camera inspection ..."
A few years later, in Nixon v. Fitzgerald, 457 U.S. 731 (1982), the Supreme Court held that "a former President of the United States is entitled to absolute immunity from damage claims predicated on his official acts" and that this "absolute Presidential immunity from damages liability" extends to all official acts, even those within the "outer perimeter" of his official responsibility.
More recently, in Clinton v. Jones, 520 U.S. 681 (1997), the Supreme Court recognized that while the President has absolute immunity from damages claims arising out of official acts extending to the "outer perimeter of his authority" (citing Nixon v. Fitzgerald), that immunity does not extend to claims arising prior to the President being elected; however, "With respect to acts taken in his 'public character' - that is, official acts - the President may be disciplined principally by impeachment, not by private lawsuits for damages."
So it is settled law that a President has absolute immunity from damages claims arising out of official acts extending to the outer perimeter of his authority, but does not have absolute immunity for purely private actions, taken before or after office or, presumably, during office if they have nothing to do with his official duties (e.g., Clinton could have been prosecuted or sued for sexually assaulting Kathleen Willey in the oval office).
The only open issue in Trump's case is whether the President's absolute immunity extends to criminal prosecution arising out of official acts "extending to the outer perimeter of his authority," or whether the President's absolute immunity is limited to civil claims for damages. My bet is that the Supremes will recognize Presidential immunity from criminal prosecutions arising out of official acts, or local district attorneys in both Democrat and Republican controlled districts will be constantly indicting and prosecuting Presidents and former Presidents of the opposite party, using the templates created by the Democrats trying to prevent Trump from being re-elected. OTOH, I think Roberts will try to make the opinion as narrow as possible, to avoid a 5/4 or 6/3 decision.
Nixon needed immunity from the CIA operation that was Watergate.
They just used different method than 1963 to continue to run things.
Someday maybe the average American will wise up to the reality that the intelligence/law enforcement/legal aspects of Government, in conjunction with big Corporations, are running all of it.