Under the United States Constitution, the President of the United States is the head of state and head of government of the United States. As chief of the executive branch and head of the federal government as a whole, the presidency is the highest political office in the United States by influence and recognition. The president is also the commander-in-chief of the United States Armed Forces. The president is indirectly elected to a four-year term by an Electoral College (or by the House of Representatives should the Electoral College fail to award an absolute majority of votes to any person). Since the ratification of the Twenty-second Amendment to the United States Constitution in 1951, no person may be elected President more than twice, and no one who has served more than two years of a term to which someone else was elected may be elected more than once. Upon the death, resignation, or removal from office of an incumbent President, the Vice President assumes the office. The President must be at least 35 years of age and a "natural born" citizen of the United States.