Sen. Hillary Clinton's decision to end her historic bid for the White House and ceding the Democratic nomination to Sen. Barack Obama, ends a long, often bitter battle for the right to challenge Sen. John McCain, R-Ariz., in the general election.
Obama, D-Ill., who claimed victory after clinching the necessary delegates on Tuesday, will be the nation's first African American running with the nomination of one of the country's two major political parties.
Clinton quickly emerged as the formidable frontrunner, raising millions of dollars and leading in both state and national polls.
In an ABC News/Washington Post poll conducted in December 2006, she was supported by 39 percent of Democrats and Democratic-leaning independents, well ahead of her nearest competitors -- Barack Obama with 17 percent support; former Sen. John Edwards, D-N.C., with 12 percent; and former Vice President Al Gore, 10 percent.
Obama had announced his intention to form a presidential exploratory committee a few days before Clinton's announcement on her Web site, hillaryclinton.com.
Just weeks later, standing outside Illinois' historic Old State Capitol building where Abraham Lincoln gave a famous speech condemning slavery and calling for the United States to unite, Obama, then a 45-year-old with just two years of federal legislative experience under his belt, officially announced his longshot bid.
"I recognize there is a certain presumptuousness in this, a certain audacity," Obama said to the crowd of 16,000 braving a freezing February afternoon. "I know that I haven't spent a lot of time learning the ways of Washington. But I've been there long enough to know that the ways of Washington must change."
Clinton dominated a crowded field of Democratic candidates including Obama, Edwards, as well as Sens. Joe Biden of Delaware and Chris Dodd of Connecticut, Ohio Rep. Dennis Kucinich, Gov. Bill Richardson of New Mexico, former Iowa Gov. Tom Vilsack and fomer Sen. Mike Gravel of Alaska, for much of the summer and early fall of 2007.
In an interview with ABC News' "Nightline" in September 2007, Clinton chief strategist Mark Penn confidently predicted, "I believe she's going to be the nominee. I think every day is a good one, and I think that as every day goes on people see that she has the strength and experience to become president."
There was reason for optimism: Clinton had survived nearly the entire year as the Democratic frontrunner and none of her opponents seemed to be gaining major traction. But that trend was about to change.
At a Halloween debate on Oct. 31, 2007, chinks in Clinton's armor appeared.
Sharply challenged by Obama and Edwards on Iraq, free trade and illegal immigration, Clinton said a New York State proposal supported by then-Gov. Eliot Spitzer to give driver's licenses to illegal immigrants "makes a lot of sense."
Critics and the other candidates pounced and Clinton later admitted she "wasn't at (her) best" during the debate.
Ten days later, Obama outshined Clinton at Iowa's Jefferson-Jackson dinner in Des Moines and both candidates seemed to increase the rhetoric of the race.