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.
2008 United States elections
Senator Barack Obama of Illinois was the Democratic nominee, and Senator John McCain of Arizona was the Republican nominee. Incumbent President George W. Bush was ineligible for re-election per the 22nd Amendment, which limits a president to two terms, and incumbent Vice President Dick Cheney declined to run for the office.