John McCain, the senior United States Senator from Arizona, staged his second candidacy for the presidency of the United States for the 2008 presidential election. His candidacy was in the works for a number of years, was informally announced on February 28, 2007 and then formally announced on April 25, 2007.

Should McCain win in 2008, he would be the oldest person to assume the Presidency in history at initial ascension to office, being 72 years old and surpassing Ronald Reagan, who was 69 years old at his inauguration following the 1980 election.

He has dismissed concerns about his age and past health concerns (malignant melanoma in 2000), stating in 2005 that his health was "excellent." In the event of his victory in 2008, he would also become the first President of the United States to be born in a U.S. territory (the Panama Canal Zone) outside of the current 50 states, and the first sitting U.S. Senator since John F. Kennedy to win the presidency.

Source: Wikipedia