The significance of President Nixon's "enemies list" was that it helped to show that Nixon was prone to using the powers of his office for improper ends. The enemies list was a list of people that Nixon wanted harassed in various ways. They would be subject to things like tax audits that were meant solely to make life difficult for them because of the fact that they were opposed to Nixon. This is a completely improper use of presidential power. When the existence of the list was revealed during the Watergate hearings, it served to show Nixon's unscrupulousness and his willingness to use his official powers for improper ends.