John Sidney McCain (born August 29, 1936) is the senior U.S. Senator from Arizona, having served since 1987. He first became a national celebrity after being held as a prisoner of war for five and a half years in Vietnam. He was a presidential candidate in the 2000 election, but was defeated in the Republican primary by George W. Bush. On 15 November 2006, McCain announced he was forming an exploratory committee for a 2008 presidential campaign.