At the federal level, the impeachment process is a three-step procedure.
First, the Congress investigates. This investigation typically begins in the House Judiciary Committee, but may begin elsewhere. For example, the Nixon impeachment inquiry began in the Senate Judiciary Committee. The facts that led to impeachment of Bill Clinton were first discovered in the course of an investigation by Independent Counsel Kenneth Starr.
Second, the House of Representatives must pass, by a simple majority of those present and voting, articles of impeachment, which constitute the formal allegation or allegations. Upon passage, the defendant has been "impeached".
Third, the Senate tries the accused. In the case of the impeachment of a president, the Chief Justice of the United States presides over the proceedings. For the impeachment of any other official, the Constitution is silent on who shall preside, suggesting that this role falls to the Senate's usual presiding officer, the President of the Senate who is also the Vice President of the United States. Conviction in the Senate requires a two-thirds supermajority vote of those present. The result of conviction is removal from office.
