"By contrast, Nixon began 1973 as a president reelected with an overwhelming majority and winning 49 states. He stood at 68 percent approval. Two weeks before his second inauguration, Watergate burglars pled guilty to conspiracy and other crimes, which soon triggered congressional inquiries into Watergate. By May, when the Senate Watergate hearings began, Nixon’s standing in public opinion began to erode, a decline accelerated at each stage by his stonewalling of Congress and the courts. Public support for impeachment of Nixon, however, did not reach the level at which it already stands for Trump until near May 1974, a full year after the Senate Watergate hearings. In short, Trump now stands in public opinion where Nixon did after Senate hearings, after John Dean and others testified, after the Nixon tapes were exposed."
https://www.justsecurity.org/64057/an-open-memo-comparison-of-clinton-impeachment-nixon-impeachment-and-trump-pre-impeachment/
And HERE is Pew Reseach - showing the 19% I quote:
https://www.pewresearch.org/fact-tank/2014/08/08/how-the-watergate-crisis-eroded-public-support-for-richard-nixon/