The following is a timeline of major events leading up to and immediately following the United States presidential election of 2008. The election was the 56th quadrennial United States presidential election. It was held on November 4, 2008, but its significant events and background date back to about 2002. The Democratic Party nominee, Senator Barack Obama of Illinois, defeated the Republican Party's nominee, Senator John McCain of Arizona.

2002 October 2002 October 2 – Columnist Maureen Dowd writes an article in The New York Times entitled "Can Hillary Upgrade?", which claims that former First Lady Hillary Clinton, serving as the junior United States senator from New York, has softened her criticism of the then-pending invasion of Iraq because "Clinton knows that any woman who hopes to be elected president cannot afford to be seen as too much of a dove", and that she might seek the Democratic Party's nomination in 2008.

2003 November 2003 November 27 – In an interview with the German magazine Bunte, Hillary Clinton states that she will not be a candidate for the presidency in 2004, and when told that some were disappointed with that decision, replies "I know. Well, perhaps I'll do it next time around." This is interpreted to mean that she will consider a run in the 2008 race, if the 2004 Democratic nominee is unsuccessful.

2004 July 2004 July 27 – Illinois State Senator and United States Senate candidate Barack Obama delivers the keynote address at the Democratic National Convention. After the speech, MSNBC's Chris Mathews praises Obama's performance and predicts that he will someday be the nation's first African American president saying "I have seen the first black president there".

November 2004 November 2 – President George W. Bush wins re-election defeating Senator John Kerry in the 2004 United States presidential election. November 9 – Following John Kerry's loss in the 2004 election, Cameron Kerry, John Kerry's brother and political confidante states in regards to another presidential run "That's conceivable... I don't know why that [last week's loss] should necessarily be it. I think it's too early to assess. But I think that he is going to continue to fight on for the values, ideals, and issues this campaign is about."

2005 February 2005 February 7 – After the second inauguration of George W. Bush, in an interview with Fox News Sunday, Vice President Dick Cheney is asked whether he will seek the Republican nomination for the presidency in 2008. He replies "I've got my plans laid out, I'm going to serve this president for the next four years and then I'm out of here." When pressed further, Cheney responds to a potential presidential run by stating "Not only no, but hell no" and quotes General William Tecumseh Sherman's famous statement "If nominated, I will not run. If elected, I will not serve."

2006 March 2006

March 11 – The 2006 Southern Republican Leadership Conference Hotline Straw Poll is won by Senate Majority Leader Bill Frist with 36.9 percent of the vote. March 21 – United States senator and 1988 presidential candidate Joe Biden of Delaware announces that he will seek the Democratic nomination in 2008.

April 2006 April 17 – Former United States Senator Mike Gravel of Alaska states his intention to run for the Democratic presidential nomination a speech before the National Press Club.

May 2006 May 20 – The Wisconsin State Republican Convention Straw Poll is won by United States Senator George Allen of Virginia, with 17.4 percent of the vote. May 22 – Senator Christopher Dodd of Connecticut tells The Hartford Courant that he has "decided to do all the things that are necessary to prepare to seek the presidency in 2008."

October 2006 October 12 – Former Democratic Governor of Virginia Mark Warner states that he will not seek the presidency in 2008. October 22 – Despite having stated that "I can unequivocally say I will not be running for national office in four years", Senator Barack Obama of Illinois states in relation to a presidential run "I don't want to be coy about this: given the responses that I've been getting over the last several months, I have thought about the possibility, but I have not thought about it with the seriousness and depth that I think is required ... After November 7, I'll sit down and consider, and if at some point I change my mind, I will make a public announcement and everybody will be able to go at me." October 30 – Massachusetts Senator John Kerry makes a "botched joke" about education and the Iraq War, which dominates the news for several days. Republican Representative Duncan Hunter of California announces the formation of an exploratory committee for a presidential run.

November 2006 November 9 – Outgoing Democratic Governor of Iowa Tom Vilsack announces that he will be a candidate for the Democratic nomination. November 10 – Republican Senator John McCain of Arizona announces the formation of a presidential exploratory committee. Rudy Giuliani, the former Republican Mayor of New York City, forms a presidential exploratory committee. November 12 – Wisconsin Senator Russ Feingold, a prominent member of the Democratic Party's progressive wing, withdraws his name from the race. November 15 – Former Republican Governor of Wisconsin and Secretary of Health and Human Services Tommy Thompson announces that he intends to form a presidential exploratory committee in early 2007. November 29 – Republican Senator and Senate Majority Leader Bill Frist of Tennessee withdraws his name from the race. November 30 – Tom Vilsack announces that he is running for president.

December 2006 December 1 – Democratic Senator Evan Bayh of Indiana announces the formation of an exploratory committee. On The Tonight Show, Democratic Senator Barack Obama of Illinois states he is considering running for president. December 2 – Former Democratic Senator and former Senate Minority Leader of South Dakota Tom Daschle withdraws his name from the race. December 3 – Democratic Senator Hillary Clinton begins discussions with New York Democratic officials to indicate the possibility of a 2008 presidential campaign and to ask for their support if she does. December 4 – Republican Senator Sam Brownback of Kansas announces the formation of an exploratory committee. December 9 – Republican Senator George Allen of Virginia, who had lost a close campaign for re-election to Jim Webb, announces that he will not run for president. Democratic Governor of New Mexico Bill Richardson states that he will decide in January whether to form an exploratory committee. December 11 – Democratic Representative and 2004 presidential candidate Dennis Kucinich of Ohio announces his plans to run for president in a report by the Associated Press. December 16 – Democratic Senator Evan Bayh of Indiana withdraws from the race, citing his status as "a relatively unknown candidate". December 17 – Former Democratic Senator, 2004 presidential candidate and 2004 vice presidential nominee John Edwards of North Carolina announces he will formally begin his candidacy later in the month. December 19 – Former Virginia Governor Jim Gilmore announces he is setting up an exploratory committee, saying that he is a "Reagan Republican." December 28 – John Edwards officially launches his campaign in New Orleans, Louisiana, following an Internet glitch causing his website to announce his candidacy earlier than planned.

2007 January 2007

January 1 – Republican candidate Rudy Giuliani's campaign strategy is made public in the New York Daily News. Giuliani claims the material was stolen while the News claims it was left in a hotel accidentally. January 3 – Outgoing Republican Governor of Massachusetts Mitt Romney sets up a presidential exploratory committee. January 5 – Republican Senator Sam Brownback of Kansas's exploratory committee announces his campaign will officially start on January 20. January 7 – Democratic Senator Joe Biden of Delaware declares he is running, and will set up an exploratory committee later in the month. January 9 – Civil rights activist and 2004 Democratic candidate Al Sharpton says that he is considering another run for president. January 11 – Democratic Senator Christopher Dodd of Connecticut officially announces his candidacy. Republican Representative Ron Paul of Texas announces the formation of a presidential exploratory committee. The Democratic National Committee announces that it will hold its 2008 National Convention in Denver, Colorado. January 15 – Republican Representative Tom Tancredo of Colorado establishes an exploratory committee. January 17 – Democratic Senator Barack Obama of Illinois announces that he is forming an exploratory committee. January 20 – Democratic Senator Hillary Clinton announces that she is forming an exploratory committee. Republican Senator Sam Brownback of Kansas officially announces his candidacy for the 2008 Republican presidential nomination in a rally in his home state. January 21 – Democratic Governor Bill Richardson of New Mexico announces the formation of a presidential exploratory committee. January 24 – 2004 Democratic nominee John Kerry rules out a presidential run to seek re-election to his United States Senate seat. January 25 – Republican Representative Duncan Hunter of California formally and officially becomes a candidate. January 28 – Mike Huckabee officially announces his candidacy on Meet the Press. January 31 – Democratic Senator Joe Biden of Delaware formally and officially becomes a candidate.

February 2007

February 1 – The Democratic National Committee's annual winter meeting convenes in Washington, D.C., featuring ten presidential candidates. February 5 – Former Republican Mayor of New York City Rudy Giuliani files a statement of candidacy with the Federal Election Commission. February 10 – Democratic Senator Barack Obama of Illinois formally and officially announces his candidacy. February 13 – Former Republican Governor Mitt Romney of Massachusetts formally and officially announces his candidacy. February 21 – The first presidential forum is held in Carson City. February 23 – Former Democratic Governor Tom Vilsack of Iowa withdraws from the race, citing money problems. February 28 – Republican John McCain of Arizona states that he will formally announce his candidacy in April.

March 2007

March 1 – John McCain wins the Spartanburg County, South Carolina Republican Party straw poll, with 22.6 percent of the vote. March 3 – The Conservative Political Action Conference straw poll is won by Mitt Romney with 21 percent of the vote. 1,705 votes are cast. March 9 – A Nevada Democratic debate is canceled to protest editorial policies of Fox News. March 11 – Former Republican Senator Fred Thompson of Tennessee announces on Fox News that he is considering a presidential campaign. March 12 – Republican Representative Ron Paul of Texas announces his candidacy on C-SPAN. March 22 – Democratic candidate John Edwards's wife Elizabeth announces that her breast cancer has become malignant, but her husband's campaign will go on.

April 2007

April 1 – Former Republican Governor of Wisconsin and Secretary of Health and Human Services Tommy Thompson announces his presidential candidacy. April 2 – Republican Representative Tom Tancredo of Colorado announces his presidential candidacy. April 12 – Barack Obama wins a straw poll held at a virtual town hall debate between the Democratic candidates on the subject of the Iraq War, with 27.87 percent of the vote. 4,882 votes are cast. April 25–April 27 – John McCain launches his presidential campaign with stops in New Hampshire, South Carolina, Iowa and Arizona. April 26 – Former Virginia Governor Jim Gilmore formally announces his candidacy for the Republican nomination. The South Carolina Democratic Party hosts a presidential debate at South Carolina State University in Orangeburg County.