Panorama reveals how Senator Obama's campaign has been challenged by an unlikely contender, John McCain's running mate Sarah Palin.
"He is the one. He is the one!" So declared influential US chat show host Oprah Winfrey as she publicly gave her backing to Democratic presidential candidate Barack Obama in 2007.
And for some time it seemed that Oprah was right, that the man she described as having "an ear for eloquence and a tongue dipped in the unvarnished truth" was firmly on the path to becoming America's first black president.
Will McCain's gamble in choosing Sarah Palin pay off?
Obamamania swept the nation - tens of thousands turned out to hear him speak, celebrities and political heavyweights rallied to his message of change, even Hollywood heartthrob George Clooney described Barack Obama as a "rock star".
The result seemed in the bag. Mr Obama was America's new prince, waiting to replace Republican George W Bush, now the most unpopular president in US history, and claim his throne.
But as Obama and the Pitbull reports, that was all before a political hurricane made landfall in early September in the form of Sarah Palin.
Faced with the buzz surrounding Mr Obama and his message of change, his Republican rival John McCain took a gamble and made the little-known Alaska governor his surprise vice-presidential pick - a choice which could make or break his campaign.
Now with just weeks to go before election day on 4 November, Mr Obama is ahead in most national polls, but in the swing states which hold the key to election victory the result is still too close to call.
Though clearly very different in both their backgrounds and political affiliations, Mr Obama and Mrs Palin have each experienced a meteoric rise from local politics to the threshold of the White House.
For each their personal story has been a key part of their appeal.
In Obama and the Pitbull, BBC News America presenter Matt Frei takes a closer look at those stories.
Mr Obama has made much in speeches of the fact that he is the son of a Kenyan man and a white woman from Kansas - a story which plays to the traditional American ideals of self-reliance and aspiration.
But Sarah Palin has been cast in the role of a classic American hero too - the mythic frontierswoman - and in doing so the moose-shooting, self-styled "pitbull in lipstick" and mother of five has re-energised the US' conservative heartland.
The real Obama
Panorama travels to two very different Americas - Obama's political home in South Chicago, and the crucial battleground state of Ohio - to see how the different versions of America offered by the Obama-Biden team and the McCain-Palin team are playing out.
The economic turbulence has benefited Obama's campaign
He examines the astonishing trajectory of Mr Obama's political career, which has seen him go from his first public office to presidential candidate in just 12 years.
And he tries to find out who the real Barack Obama is:
Is he, as some in the programme say, a neophyte, with nothing on his CV which qualifies him for the role as president?
Is he a scheming careerist, whose choices of friends, mentors and even which church to attend all come down to climbing the political ladder?
Or is he the real deal and America's best hope in a troubled time?
The programme also examines the way in which Mr Obama and his supporters have broken the political mould, recruiting new voters from parts of the electorate previously thought unreachable and smashing all fund-raising records.
Through nimble use of the internet the Obama campaign has collected huge numbers of small on-line donations, a success which has been tied to his calls for a complete overhaul of the way American politics are funded.
Matt Frei witnesses Obama's ability to inspire firsthand
But as Obama and the Pitbull asks - is it quite the revolution which has been suggested, or is Mr Obama's campaign war chest, like that of his Republican rival John McCain, still heavily reliant on large sums from Corporate America?
With global economic turmoil now engulfing Wall Street Corporate America observers say that the next US leader - be it Mr McCain or Mr Obama - will face the most difficult day one agenda of any president in history.
The turbulence has boosted support for Mr Obama, who appeared to remain calm while the the economy was having a nervous breakdown.
In contrast, Mr McCain's approach looked chaotic as he dramatically suspended his campaign then reinstated it.
And his trump card - Mrs Palin - has seemed out of her depth, causing many to view Mr McCain's choice as reckless more reckless than decisive.
In Obama and the Pitbull, Panorama assesses whether Mr Obama is at last home and dry.
At this point the polls suggest the presidency is Mr Obama's to lose, but it is still all within the margin of error.