The US Constitution: Article 2, Section 4

The President, Vice President and all civil Officers of the United States, shall be removed from Office on Impeachment for, and Conviction of, Treason, Bribery, or other high Crimes and Misdemeanors.

 It makes you wonder if getting a quickie really counts as a high crime or misdemeanor... I suppose it was really the fact that he lied... Whatever...