In the United States, the presidential impeachment process begins when the House Judiciary Committee decides that the President has acted in such a way that a vote for impeachment is warranted. If a majority of the House of Representatives votes in favor of impeachment, the President is subject to a trial deciding their ability to remain in office.
The U.S. Constitution gives the House of Representatives sole discretion over the process of invoking the Articles of Impeachment when the Judiciary Committee deems that the President is guilty of sufficient wrongdoing, through a series of hearings. Under the Constitutional standard this may include crimes or misdemeanors, failure to execute the role presidential office or simply behavior that Congress decides is unacceptable.
The grounds for impeachment are debated in the House of Representatives to evaluate all aspects of the President's case before being brought to a vote. When the House of Representatives votes to invoke impeachment, the Senate presides over a trial to decide whether the President is guilty of sufficient offenses to warrant removal from office. The Senate require a two-thirds voting majority to remove a sitting President from office under impeachment rules.
As of 2015, only three standing Presidents have been successfully impeached, with two being acquitted by the Senate and the third, President Nixon, resigning before he could face a full Senate trial.