Under Article I, Section 5, clause 2, of the Constitution, a Member of Congress may be removed from office before the normal expiration of his or her constitutional term by an “expulsion” from the Senate upon a formal vote on a resolution agreed to by two-thirds of the Members of that body present and voting.
While there are no specific grounds for an expulsion expressed in the Constitution, expulsion actions in both the House and the Senate have generally concerned cases of perceived disloyalty to the United States.
Since 1789, the Senate has expelled fifteen members.