Impeaching a American President is rare. It’s only happened twice in American history — to Presidents Andrew Johnson and Bill Clinton — and neither of those times resulted in a president being removed from office. However, the question of impeachment once again looms large in some corners of American politics.

To be impeached, a President or other federal official must have committed one of the violations described by the Constitution as “treason, bribery, or other high crimes and misdemeanors.” But history shows that if a President is to be impeached, the biggest factor may be political will — whether members of a President’s own party are willing to turn against him, and whether enough members of Congress believe that trying to remove the President is worth the risk of losing popular support.

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