The Constitution defines impeachable offenses as "treason, bribery, or other high crimes and misdemeanors". The meaning of the last phrase has always been in doubt, and is open enough to cover almost anything that the Congress decides. Those that are impached besides the President and Vice President are all Civil Officers. Who are Civil Officers and do they include Congress has always been in dispute, but in practice since each chamber of Congress can expell its own members they have used that method.

The Congress has impeached Presidents twice . Preisident Johnson and President Clinton. In both cases the House of Representatives impeached but the Senate did not convict, thus the President remained in office. One Supreme Court Justice Samuel Chase was impeached but he too was not convicted by the Senate. Fourteen federal judges have been impeached, of them seven have been convicted and removed by the Senate.