The crowd could sense history in the warm Florida air. The assembled thousands wanted to see the man who stands on the brink of being the first black President of the United States.

Dan Bernard, 49, had brought his three young nephews and nieces. They had driven for hours to attend Barack Obama's rally in the city of Sunrise. "I wanted them to see history. I want them to look back when they are grandparents and be able to say, 'I was there'," Bernard said.

It was a common sentiment. Obama himself shared it. "At this defining moment in history, you can give this country the change we need," he told the cheering throng.

One of the most extraordinary elections ever fought has brought the American people to within two days of casting their vote. They will either elect a young, liberal black senator from Chicago or an old, conservative war hero.

Their choice will affect the entire world.

Obama has brought a touch of the rock star to US politics. He has appeared before crowds of 100,000 or more. He has raised more money than any other presidential candidate in history. His candidacy has more resembled a social movement than a political campaign.

It could end by making a black American the most powerful man in the world and signal a once-in-a-generation change in America.

"He's black and he's got a Middle Eastern-sounding name. Yet the country is positioned to vote for him for President.

That's enormous," said Professor Seth Masket, a political scientist at the University of Denver.

But it is not over quite yet. John McCain and the Republican Party remain in the race. They are behind in the polls in the battleground states, but the gap has narrowed recently.

McCain has struck a fiercely populist note and he knows how to fight. All his great triumphs - in war and in politics - have come against the odds. "Nothing is inevitable here. We never quit. We don't hide from history. We make history," he told an enthusiastic crowd in Mentor, Ohio, last week. His beaming grin showed that he believes he can do it.

But it will not be up to him. This race will be decided by tens of millions of Americans at the polls. Only then will the watching world know if the greatest election in recent history has a final twist in its tale.

The election has already been an epic for Obama. His quest for the White House began what seems like an age ago. In February 2007, at the "winter meeting" of the Democratic National Committee in Washington's Hilton Hotel, each Democratic hopeful gave an introductory speech to a crowd of activists. They laid out their stall. Obama's stood out only because it was so bare compared with his ribbon-draped rivals'. There were no placards. No badges or posters. Just a sign-up sheet and a few pens on a desk manned by two young volunteers.