In the end, I think that the Watergate Scandal played a decisive role in the resignation of Richard Nixon. The event itself, the cover up that followed, and the revelation of the unsavory nature of the Nixon Presidency all significantly damaged the President's credibility. The Watergate Scandal made the President weak from a political point of view. The President lacked credibility with the American public to pass legislation and act as Commander-in-Chief. Regardless of the fact that he won a second term with a resounding majority, the Watergate Scandal took its toll on how Americans viewed their President. With mounting criticism from the public and legislative investigations, a Constitutional crisis began to mount.
Additionally, the perception from foreign nations was that Nixon would not be able to weather the Watergate storm, making negotiations with other nations very difficult. In the end, the Watergate Scandal resulted in the resignation of the President as criticism began to mount and members of the legislative branch were preparing to undoubtedly impeach the President. In avoidance of this fate, resignation seemed to be the only option.