How did the Watergate scandal affect the reputation of President Nixon?

Simply put, Watergate completely destroyed Nixon's reputation. For many years, political opponents had alluded to his penchant for dirty tricks, but few people thought he would stoop so low as to break the law and violate the Constitution he had sworn to uphold.
Nixon had been reelected in 1972 in a massive landslide victory over his Democratic opponent, George McGovern; he had achieved a notable foreign policy success in establishing good relations with Communist China. Yet, Nixon's paranoia and chronic insecurity meant that he could never feel truly comfortable in his own skin. In particular, he believed that the press were uniformly hostile and out to get him. Even though he had just roundly defeated the Democrats in the race for the White House, he still did not hesitate in authorizing illegal wiretaps to be used against them.
Nixon's reputation was destroyed by Watergate for two main reasons. First, the President had clearly broken the law. The head of state, despite Nixon's loud protestations to the contrary, was a criminal. Secondly, he not only authorized illegal acts against his opponents, he actively tried to cover them up. Nixon's long-standing reputation for dishonesty now began to catch up with him. Even those who had overlooked his duplicitous behavior in the past realized that this was a much more serious and much more dangerous situation.
https://www.history.com/topics/1970s/watergate