I can’t speak specifically to the Nixon situation, but I feel this answer is still pretty relevant.

A major aspect to keep in mind when discussing any extra-legal practice on the part of the federal government is that, just because they get caught and apologize, doesn’t mean they stop doing it. This is admitted to on record in many cases but is most notable in the instance of the COINTELPRO of the FBI during the late 1950s, 1960s, and into the 1970s. These blatantly illegal and often lethal practices by the FBI of false arrests, imprisonments, guerilla propaganda campaigns, misinformation campaigns, and assasinations have been exposed in many different books and writings. However these practices continued despite the claims by the FBI that the practices had stopped and they had changed their methods. This practice is true of much of the executive branch departments and agencies, I’m sure presidential administrations would approach issues similarly.