US Elections: The Transformation of Barack Obama

It was, as nearly everyone among the thousands of jubilant supporters recognized, a little slice of history.

Barack Obama, once seen as a most improbable presidential candidate, before their eyes had been declared the Democratic nominee and the first African-American to have a real shot at winning the White House.

But what was not quite as apparent was that 16 months of a campaign about change had also transformed the candidate.

"America, this is our moment. This is our time, our time to turn the page on the policies of the past," Obama told the crowd, and the thousands inside the arena went wild, swallowing up his next few sentences with their cheers.

And then Obama seized his moment, pivoting swiftly from his battle against the now-defeated Hillary Clinton for the Democratic leadership to rattle off a series of attacks against John McCain, his likely Republican opponent next November.

Obama's appearance here tonight was far more than a victory rally of a winning candidate. Several people in the crowd said they were moved by the sense of history about the occasion - and by Obama's promise of change.

"Yes, we can," they chanted furiously, picking up the message of hope from the early days of the race.

In the shadow of the television camera risers, campaign volunteers danced to Stevie Wonder music, and hugged. Others talked about how unlikely it had seemed, all those months ago, that Obama could ever be the nominee.

But as an email from McCain's campaign went out to reporters headlined: "the general election begins tonight."

And so it did. Obama began with a rare mention of the grandmother who raised him, and who lives in Hawaii. "She poured everything she had in me and helped make me the man I am today," he said. "Tonight is for her."

Then he unveiled a much steelier persona than before. In a sign of the coming general election fight, Obama talked about "tough" diplomacy, and about putting pressure on Iraq's leaders.

His soaring message of the early days was brought firmly down to earth with stories of workers in Pennsylvania who had lost their jobs and couldn't afford the fuel costs to look for a new one.

It was a messy night too - although the crowds had no way of knowing it. At about 9pm, while the screens had switched to testimonials from Obama supporters across the country and the Change video of Will.i.am, Hillary Clinton was being declared the winner of the South Dakota primary.

Minutes later, Clinton gave a speech to her supporters in New York touting the nearly 18m votes she had won. Had they known, Obama's supporters here might not have been so charitable.

Taking a cue from Obama's conciliatory speech, they cheered Clinton three or four times. A number of women in the crowd said they would always admire the example she set of tenacity.

Officially, the Obama camp is hoping that Clinton's tenacity might wear off a bit now that the general election is at last underway.

"I know she will handle this elegantly like she always does, and I know that we will be united as a party," said Amy Klobuchar, the Democratic senator from Minnesota.

David Axelrod, Obama's chief strategist, also paid tribute to Clinton's passion.

For the moment though Clinton remains in the political frame - although few people at the rally in St Paul tonight were willing to give her more than a passing thought.

More than 20,000 people filled the stadium to hear Obama - its largest crowd ever. An additional 15,000 watched on giant television screen outside.Somewhere among the crowd in the arena as Obama spoke, Greg Adkins quietly shed a few tears.

"It was great, and it was historical, and it was really significant," said Adkins, an engineer from the suburban town of Stillwater who is African American. "I'm a lifetime Republican, and I was touched and moved."

As the crowd filed out of the arena, he still occasionally dabbed at his eyes.

"That certainly touches me that he's African American. That really speaks deep in my heart," he said. "I hope it speaks to the African-American community that "yes, we can'."