By Kevin Connolly
BBC News, Columbia, South Carolina
Few politicians can generate the buzz that surrounds Barack Obama
A British politician once remarked that a week is a long time in politics - well, this week has seemed like an eternity in the life of the Municipal Convention Centre in Columbia, South Carolina.
Last week, in one of its smaller side chambers, we watched the supporters of the Republican hopeful Mike Huckabee slowly come to terms with the realisation that he had failed to secure the victory he needed to keep his presidential campaign on track.
It was a flat affair, with only an occasional untethered balloon drifting around the room to remind you that it was meant to have been a victory rally.
This week, the convention centre's cavernous main arena played host to the extraordinary event at which Democrat Barack Obama and his supporters celebrated the victory in South Carolina that means his run for the White House is still on track.
Few politicians anywhere can generate the kind of buzz that surrounds Mr Obama.
A cheering, chanting queue waited patiently in the darkness for the doors to open, and hundreds were shut outside when the doors were closed more than an hour before he spoke.
Inside, the main hall was a place of deafening passion and colour, pulsating with enough energy to send a permanent tremor through the metal terracing on which the world's TV crews were perched.
'Yes we can'
It is not clear how the energy of these events translates into the more conventional political process, but they are extraordinary for their vitality - the crowd was rock-concert-meets-cup-final more than political gathering.
Mr Obama's campaign has attracted support from a wide mix of people
But, make no mistake, there were plenty of serious political issues at stake in South Carolina.
The composition of the crowd in itself was fascinating - there were plenty of young white people mixed in with the African-Americans of all ages, and there were older white people too joining in the call-and-response chant which has come to characterise the Obama campaign.
A single voice calls out a question: "Fired Up?... and thousands of voices chant back "Ready to Go!".
When they tire of that, they chant an answer to the great question of 2008 - can they win the White House?
Their answer is simple - they roar out "Yes we can".
In the cauldron intensity of the event, it is easy to believe them, but the figures from South Carolina merit closer attention.
We expected that Senator Obama would win the state because it was clear that he had the support of a majority of the black voters who make up half the Democratic electorate, and he duly did.
It was an overwhelming victory too - he finished with 55% of the vote, against 27% for Hillary Clinton and just 18% for John Edwards, who may now have to accept that his campaign is doomed.
The challenge for Mr Obama was to show an ability to reach out beyond the core demographic on which he can rely.
After all, he doesn't want to be a black candidate for the presidency - he wants to be a candidate offering genuine change who just happens to be black, and that's a very different thing.
The figures offer him some encouragement, but maybe not quite as much as he might have hoped.
He won 78% of the black vote, and 24% of the white vote.
To make an impact in the hugely influential states which vote on Super Tuesday, like California and New York, he would have to do better than that, but his supporters noisily assured me that the momentum from South Carolina would help to change all that.
That may be optimistic.
Super Tuesday focus
The Clinton campaign packed up its tents and stole off into the night before the results in South Carolina were even declared.
Mrs Clinton is already campaigning hard in Super Tuesday states
The scale of the defeat meant the best strategy was to move on to the Super Tuesday states and start working for victory, instead of remaining in South Carolina and contemplating defeat.
So at about the time when Mr Obama's poetry-suffused rhetoric about change was raising the roof in Columbia, Senator Clinton was already hard at work in Tennessee, talking about health care and mortgage rates and the cost of going to college and the other things that trouble American families.
Polls in key states at stake on Super Tuesday show her ahead.
The battle in the Democratic Party has a long way to go, partly because its system awards each candidates a share of the delegates to the nominating convention according to their share of the vote in each primary.
Losing narrowly is still a good result under this system... and it means it is perfectly possible for the contest between Mr Obama and Mrs Clinton to go on for several months yet, especially if Mr Edwards is forced out in the near future.
That would leave the Democratic race as a straight fight between two candidates who offer a historic choice to America - the first black leader, or the first woman president.
Long way to go
Mrs Clinton has herself made the point that it would mark an extraordinary change in the status of women in America and beyond if she were to win.
But I thought I'd leave the case for the election of the first black president to John Hurley, a white Vietnam veteran I met in the crowd at that convention centre in Columbia.
He had travelled from Massachusetts to be there and said he had always hoped, rather than believed, he would live to see a black presidential candidate running with a real chance to win.
Mr Hurley told me: "It's what makes this a transformational election. This is something different. He's not a fringe candidate, he's a mainstream candidate.
"He has lit this country on fire, he has inspired this country. Every place you go, he is turning out crowds that Hillary Clinton cannot match, that John Edwards cannot match. It's magical and it's wonderful for the country and for the world."
After South Carolina, the Obama supporters are starting to believe again, but there is a very long way to go.