The chief justice of the United States is the chief judge of the Supreme Court of the United States and is the highest-ranking officer of the federal judiciary. Article II, Section 2, Clause 2 of the Constitution grants plenary power to the president to nominate, and, with the advice and consent of the Senate, appoint "Judges of the Supreme Court", who serve until they die, resign, retire, or are impeached and convicted. The existence of a chief justice is only explicit in Article I, Section 3, Clause 6 which states that the chief justice shall preside over the impeachment trial of the president; this has occurred three times, for Andrew Johnson, Bill Clinton, and for Donald Trump's first impeachment.