The 2008 presidential campaign of John McCain, the longtime senior U.S. Senator from Arizona, was launched with an informal announcement on February 28, 2007, during a live taping of the Late Show with David Letterman, and formally launched at an event on April 25, 2007. His second candidacy for the Presidency of the United States, he had previously run for his party's nomination in the 2000 primaries and was considered as a potential running mate for his party's nominee, then-Governor George W. Bush of Texas. After winning a majority of delegates in the Republican primaries of 2008, on August 29, leading up to the convention, McCain selected Governor Sarah Palin of Alaska as his running mate for Vice President. Five days later, at the 2008 Republican National Convention, McCain was formally selected as the Republican Party presidential nominee in the 2008 presidential election.

From January 3 to June 3, 2008, voters of the Republican Party chose their nominee for president in the 2008 United States presidential election. Senator John McCain of Arizona was selected as the nominee through a series of primary elections and caucuses culminating in the 2008 Republican National Convention held from Monday, September 1, through Thursday, September 4, 2008, in Saint Paul, Minnesota. President George W. Bush was ineligible to be elected to a third term due to the term limits established by the 22nd Amendment.