Nixon didn't know about the break-in beforehand. Certainly he should not have attempted to cover up for Haldeman and Ehrlichman who may have known. Nixon was earler let down terribly by Eisenhower (who was not exactly known for backing subordinates, remember Patton?). Nixon saved himself via the "Checkers" speech, and probably never forgave Eisenhower for not defending him regarding a trivial charge. Nixon was trying to be loyal to his own loyal aides and stick with them when they were under fire, and this destroyed him. The press hated him because he supported Whittaker Chambers against the left's (and the press') darling, Alger Hiss.
I stamd by my assessment.