"The Constitution gives Congress the authority to impeach and remove the President, Vice President, and other federal 'civil officers'1 upon a determination that such officers have engaged in treason, bribery, or other high crimes and misdemeanors. Impeachment is one of the various checks and balances created by the Constitution, and is a crucial tool for potentially holding government officers accountable for violations of the law and abuse of power. Rooted in various constitutional provisions, impeachment is largely immune from judicial review.2 When considering impeachment matters, Members of Congress have historically examined the language of the Constitution; past precedents; the debates at the Constitutional Convention; the debates at the ratifying conventions; English common law and practice; state impeachment practices; analogous case law; and historical commentaries. Although the term 'impeachment' is commonly used to refer to the removal of a government official from office, the impeachment process, as described in the Constitution, entails two distinct proceedings carried out by the separate houses of Congress. First, a simple majority of the House impeaches--or formally approves allegations of wrongdoing amounting to an impeachable offense, known as articles of impeachment. The articles of impeachment are then forwarded to the Senate where the second proceeding takes place: an impeachment trial. If the Senate, by vote of a two-thirds majority, convicts the official of the alleged offenses, the result is removal from office of those still in office, and, at the Senate's discretion, disqualification from holding future office. […] This report briefly surveys the constitutional provisions governing the impeachment power, examines which individuals are subject to impeachment, and explores the potential grounds for impeachment. In addition, it provides a short overview of impeachment procedures in the House and Senate and concludes with a discussion of the limited nature of judicial review for impeachment procedures."
CRS Report for Congress, R44260
Federation of American Scientists: http://www.fas.org/sgp/crs/index.html