From January 3 to June 3, 2008, voters of the Democratic Party chose their nominee for president in the 2008 United States presidential election. Senator Barack Obama of Illinois was selected as the nominee, becoming the first African American to secure the presidential nomination of any major political party in the United States. However, due to a close race between Obama and Senator Hillary Clinton of New York, the contest remained competitive for longer than expected; neither candidate received enough pledged delegates from state primaries and caucuses to achieve a majority, without endorsements from unpledged delegates (superdelegates).

The 2008 United States presidential election was the 56th quadrennial presidential election, held on November 4, 2008. The Democratic ticket of Barack Obama, the junior senator from Illinois, and Joe Biden, the senior senator from Delaware, defeated the Republican ticket of John McCain, the senior senator from Arizona, and Sarah Palin, the governor of Alaska. Obama became the first African American to be elected to the presidency, as well as being only the third sitting United States senator elected president, joining Warren G. Harding and John F. Kennedy. Meanwhile, this was only the second successful all-senator ticket since the 1960 election and is the only election where both major party nominees were sitting senators. This was the first election since 1952 in which neither the incumbent president nor vice president was on the ballot, as well as the first election since 1928 in which neither ran for the nomination.