Twenty-second Amendment to the United States Constitution
The amendment prohibits any individual who has been elected president twice from being elected again. Under the amendment, an individual who fills an unexpired presidential term lasting greater than two years is also prohibited from winning election as president more than once. Scholars debate whether the amendment prohibits affected individuals from succeeding to the presidency under any circumstances or whether it only applies to presidential elections.
United States presidential election
The final way to be elected for president is to have one's name written in at the time of election as a write-in candidate. This is used for candidates who did not fulfill the legal requirements to be pre-listed on the voting ticket. It is also used by voters to express a distaste for the listed candidates, by writing in an alternative candidate for president such as Mickey Mouse or comedian Stephen Colbert (whose application was voted down by the South Carolina Democratic Party). In any event, a write-in candidate has never won an election for President of the United States.