Three. The first was Andrew Johnson, then Bill Clinton, and most recently (as of Dec. 18, 2019), Donald Trump. To impeach a president, the House of Representatives must pass articles of impeachment (which are the set of charges against a president) by a simple majority, which is why Richard Nixon isn’t on this list—he resigned before articles of impeachment could be voted on. From there, the president is tried by the Senate. A removal from office requires a two-thirds majority vote.