Q115. "What is the impeachment process?"
A. The Constitution details impeachment in Article 1, Section 2, Article 1, Section 3, Article 2, Section 3, and Article 3, Section 2. The word "details," however, is a bit strong for what the Constitution provides. As with many things, the Constitution primarily gives us a skeleton of a process. The House brings charges for impeachment. The Senate holds a trial and votes to convict or acquit. The only way to remove a President, Vice President, or Article 3 judge is through impeachment. Impeachments are not tried by a jury. The rest of the process is left to the rules of Congress.
The process begins with the House. It votes on passing articles of impeachment against a member of the Executive or Judicial branches. If the articles pass, then it is said that the person has been impeached. The vote is a straight up-or-down, majority vote.
After the House votes, the impeachment goes to the Senate. There, members of the House who were advocates for impeachment become the prosecutors in the Senate trial (they are called the House Managers). The accused secures his own counsel. The judge is the Senate itself, though the presiding officer acts as the head judge. In the case of a presidential impeachment, the Chief Justice of the Supreme Court presides; in other cases, the Vice President or President Pro Tem presides.
After all testimony has been heard, the Senate votes. If the Senate votes to convict by more than a two-thirds majority, the person is impeached. The person convicted is removed from office. The Senate may also prevent that person from ever holding another elective office. The Senate may set its own rules for impeachments, and the rules are not subject to judicial review. The Senate has streamlined rules for trial of impeachment for persons holding lower offices. There is no appeal in the case of conviction of impeachment.
During the threat of impeachment of President Nixon, Charles Black wrote a book called Impeachment which details the process even further.