By Jamie Coomarasamy
BBC News, Springfield, Illinois
He took the stage with the loping stride, which already sets him apart from the crowd - his wife and two daughters by his side.
Barack Obama was met by an expectant crowd
And, as the sun began warming the crisp Illinois air, Barack Obama threw his hat into an already crowded ring.
A large, expectant crowd - many of them young - heard him formally declare that he was running for president.
Just a few months ago, the odds against an Obama campaign in 2008 were long. Now he is among the early favourites to secure the Democratic nomination.
Face of a new generation
He chose to make his announcement at a highly symbolic venue - the Capitol building in Springfield, where Abraham Lincoln delivered his famous "Divided House" speech, denouncing the divisive effects of slavery.
The son of a Kenyan father and a white Kansas mother, Obama used his address to portray himself as the multi-racial face of a new generation - a Lincoln-esque healer of a divided nation. It was well-received, by a largely sympathetic crowd.
Mr Obama faces some tough opposition
The only dissenting voices seemed to come from a group of anti-abortion activists protesting against Obama's liberal stance on this and other social issues.
The speech did not break new ground, but it did allow him to emphasise perhaps his most significant policy difference from his main rivals.
Unlike Hillary Clinton or John Edwards, the then-state senator opposed the Iraq war from the beginning.
It is a position that plays well with the Democratic base - and could be one of Obama's trump cards in the long run towards primary season. However, it does leave him open to accusations of being weak on national security.
'Ways of Washington'
He also used his speech to answer the question of his inexperience, listing some of the bills he had drawn up in the Senate and offering this wry aside: "I recognise there is a certain presumptuousness - a certain audacity - to this announcement," he said.
"I know 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."
At this initial stage in the presidential marathon, words and policies are perhaps less important than creating a positive mood and momentum. At first glance, Obama appears to have achieved both - in Springfield, at least.
Obama badges were on sale to spread the message
"His diversity gives us hope that anyone from all walks of life can achieve in this country," Springfield resident, John Harris said.
"He was amazing," another woman added. "He gives us hope. He gives me chills. It made me cry."
There is a sense that the first, embryonic stage of this campaign is now over. With a year-long slog before the primaries, Barack Obama will now face tough questions about his background, his policies and his ability to govern.
He will also have to contend with the well-funded and well-organised campaign of Hillary Clinton, not to mention that of John Edwards, New Mexico Governor Bill Richardson and a growing list of others.
But here - in the city where his political views took shape - he had his moment in the winter sun.