(Quick reference: the Watergate scandal arose from workers in Nixon's reelection campaign breaking into the offices of the Democrat National Committee, and from the subsequent effort to conceal this crime.)
Nixon committed crimes, and was made to pay the full price. By contrast, other presidents committed crimes equally serious, and perhaps more serious, and were able to escape the consequences. Why? Because Nixon failed to create the illusion of personal relationship with the American public - he failed to create the feeling, in the heart of the voters, that he was a "regular person" who was friendly and approachable. Such an impression - regardless of the reality - is important to the career of an elected politician, and the lack of this calming illusions left Nixon unprotected and left him facing the consequences of his actions.
By contrast, President Clinton was found guilty of perjury, and the government permanently removed his license to practice law - two stunning blows to a sitting president. But he remained in office. Why? His ability to project the image of a friendly, approachable "ordinary guy."
The contrast between Nixon - guilty of crimes and facing the consequences for them - and Clinton - guilty of arguable greater crimes, but given a "pass" by the public and largely shielded from the consequences of his actions - is great. Historian Barry Werth describes the "imperial" personality which ultimately cost Nixon his job:
On his last morning in power, President Richard Nixon arose in the predawn darkness after just a few hours of sleep. He ordered his favorite breakfast of poached eggs and corned-beef hash served to him, alone, in the Lincoln sitting room, the same room where twenty-two months earlier he had retreated by himself to watch on TV as he and Vice President Spiro Agnew were reelected in one of the greatest landslides in American history. The most inward, solitary, and reclusive of presidents - who paradoxically was determined to ensure that every word he spoke, and that was spoken to him, was recorded for history - Nixon to a rare degree determined exactly what he hoped to do and say in public beforehand, by himself, by filling yellow legal pads with notes, arguments, talking points, and exhortations to himself. In a few hours he would say good-bye to the people whom he most depended upon, and whom he'd most let down, betrayed, disappointed, and infuriated - his top administration, who'd served and defended him through the agonies of Watergate and Vietnam.
Nixon's last breakfast as president was on Friday, August 9, 1974. He would resign from office later that day.
It is possible to paint a sympathetic picture of Nixon - the shy introvert who had accidentally hired some unethical leaders in his campaign. Whether or not such a picture is accurate - whether or not Nixon was the criminal we understand him to be - didn't really matter in the end. What mattered was Nixon's failure to charm the American people when he needed it most - a failure due, in part or in whole, to newspaper and television coverage motivated by his political enemies - by the Democrat party eager for Nixon's political demise. They got it.