A GAFFE, they say in politics, is when someone inadvertently blurts out the truth. So it was when Joe Biden, the incorrigibly loquacious senator from Delaware, held forth about Barack Obama, his fellow aspirant for the 2008 Democratic presidential nomination.

"Look, " he declared. "You got the first mainstream African-American who is articulate and bright and clean and a nice-looking guy. I mean, that's a storybook, man."

The remark was of course profoundly politically incorrect, and profuse apologies were instantly on their way to Jesse Jackson, Alan Keyes, and Al Sharpton, all blacks who have run for the White House in recent years, and all of presumably impeccable personal hygiene and boasting impressive rhetorical skills.

But deep down, Biden was spot on. Obama, the 45-yearold junior senator from Illinois, is different. He is the first African-American candidate with a realistic chance of winning the presidency. And the reason, as Biden so clumsily made clear, is that to the white majority of the country, he hardly seems black at all.

Yesterday morning, at an open-air rally in wintry Springfield, the capital of Illinois where he spent eight years as a state senator, Obama formally launched his campaign.

The site of the announcement is laden with symbolism.

This first major black candidate of the 21st century threw his hat into the presidential ring at the old State Capitol building, in which an earlier Illinois legislator named Abraham Lincoln cut his political teeth before himself moving on to the White House, where he issued in January 1863 the Proclamation of Emancipation, freeing black slaves. This was a patented 'Only in America' moment, a testament to the country's astonishing mobility, its endless flux, and its capacity to reinvent itself.

Whether Obama can follow the path of the US's 16th and arguably greatest president is not clear. If he becomes the 44th, he will face challenges more subtle but in some respects as daunting as the Civil War - a country whose international reputation has never been lower, struggling to extricate itself from a disastrous foreign war, and whose global dominance is threatened by the ascent of China and India.

But the very fact that Obama is setting out on the road is indeed, as Joe Biden put it, "a storybook" - the climax of a meteoric career that has seen an untried newcomer, with just two years' service in the Senate, emerge as the most exciting politician of the day.

Unknown THREE years ago, he was all but unknown. Then came the electrifying keynote speech at the July 2004 Democratic convention, in which Obama told his countrymen that for all their divisions of party, race, class and social attitude, they were united by the far more important fact that they were all Americans. That November, he won a landslide victory for the vacant Illinois senate seat and was immediately touted as a presidential contender.

The only surprise is that the moment has come so soon.

But in US presidential politics, opportunity is fleeting. In this election campaign of 2008, which has already started, anything can happen.

Obama is the flavour of the hour. In most polls, he already runs second only to Hillary Clinton. In some key primary states, he is narrowly ahead.

After Springfield he travels to Iowa, whose caucuses kick off the primary season, before addressing a mass rally in his home town, Chicago. Tomorrow, he's off to New Hampshire, the key primary state which greeted him like a rock star on a visit last December.

But how long can the phenomenon last? Obama's appeal is multi-layered, yet also shallow. His background is by any standards remarkable. The son of a Kenyan father and a white Kansan mother, he was born in Hawaii - about as far away from Washington as it is possible to be born and still be eligible to run for president.

His parents (both now dead) separated a few years later, and his mother married an Indonesian. The family moved to Jakarta, where he was educated at Catholic and Muslim schools. He then returned to Hawaii, before attending the Ivy League Columbia University, and Harvard Law School, where he was the first black - and youngest ever - president of the Harvard Law Review.

This family history, coupled with a gentle manner and a political message of reconciliation and healing, make Obama one of a select group of blacks - Tiger Woods and Colin Powell are others who come to mind - who transcend race. Whites do not feel threatened by them. Rather they make Americans feel good about themselves and a society in which this sort of ascent is possible. All of which of course only makes many blacks suspicious.

African-Americans are not exactly flocking to the Obama banner. And in a sense why should they? He does not share their slave ancestry, and grew up mainly among whites. In Chicago, he did work as a community organiser on the city's poor and largely minority south side. But he has few links to the city's powerful black establishment.

The cases of Powell - the first black figure to be seriously mentioned as a future president - and Obama offer fascinating similarities and differences.

After much soul-searching Powell decided not to seek his party's nomination for 1996, even though he was the one Republican with a realistic chance of defeating Bill Clinton.

Powell demurred largely because of the opposition of his wife Alma, reflecting not least her fear that he might be assassinated. Reluctantly bowing to the inevitable, Obama's wife Michelle has given her assent this time around. But she too fears for the strains on family life and the loss of privacy for their two young daughters that the campaign will surely bring. As for assassination, suffice it to say that US politics are no stranger to violent death: look no further than the president to whom Obama is often compared, shot down in Dallas in 1963.

But there is an even more instructive footnote. In the end, of course, the Republicans chose party grandee Bob Dole to oppose Bill Clinton. Dole was soundly beaten, but an election-day exit poll in November 1996 suggested that had Powell's name, not Dole's, been on the ballot, the former would have won - not because of his appeal to blacks, who still overwhelmingly backed Clinton, but thanks to his popularity among whites. The same holds true now, for the time being.

A majority of blacks, say the polls, support Hillary, if only out of the warm glow inspired by the Clinton name. Nor should John Edwards, the third top-tier contender for the Democratic nomination, be overlooked. He is pushing a populist agenda, focused on the US's glaring social injustices, that is bound to appeal to minority voters.

Irrelevant OBAMA himself counts on sidestepping this issue by making race irrelevant. As he said last week: "If we do a good job in letting people know who I am and what I stand for, they'll make their judgement not on my race, but on how well they think I can lead the country."

There is a pristine, unsullied quality about the man that seems to lift him beyond the confines of the daily political fray - indeed the online magazine Slate has instituted an 'Obama Messiah Watch'. On Capitol Hill he stands out from his colleagues, and not only because he is the only AfricanAmerican member of the senate. When the voice reading names for a roll-call floor vote intones 'Mr Obama, ' a slight, almost delicate figure lopes forward. "At first glance, you take him for a page boy, " one veteran of the senate press gallery says.

In Washington, no significant legislative achievement bears his name - though he is on the right side of the Iraq issue as the country turns ever more strongly against the war.

Unlike Hillary, he opposed the Iraq invasion even before it was launched, and is on the record in Illinois to prove it. But having not entered the senate until January 2005, he was spared the key congressional vote of October 2002 when many Democrats, fearful of being labelled unpatriotic by the then hugely popular president before the upcoming mid-term elections, granted the White House authority to go to war. Some of those who did so, including Edwards but not yet Hillary, have been forced to repudiate their vote.

Obama does not have to.

For clues to his politics, the best place to look is Springfield, and his record in the state senate. There Obama emerged as a committed liberal - but with an ability to see both sides of the argument. He is not an ideologue but a pragmatist who worked with Republicans to fashion new campaign finance rules and a measure of healthcare reform. In extreme cases he favours the death penalty - in a state that has now imposed a moratorium on capital punishment. In short, in the classic division of politicians into warriors and healers, Obama is as emphatically the latter as George Bush is the former.

Indeed part of his appeal is the lack of a paper trail of significant votes, as he admits. "I am new enough on the political scene that I serve as a black screen on which people of vastly different political stripes project their own views, " Obama writes in his bestselling political memoir The Audacity of Hope. A short senate career is also his strength. John Kerry's 20 years in the senate bequeathed a paper trail of votes and a convoluted legislative style that probably cost him victory against George W Bush in 2004. Obama has no such 'form'. There is no risk of him making statements like: "I actually voted for the $87bn before I voted against it, " which fatally nailed Kerry as a 'flipflopper.'

As for complaints that Obama lacks the experience to lead the US in a desperately complicated world, his response is simple and devastating. The Bush administration, with the likes of Powell, Dick Cheney and Donald Rumsfeld, had perhaps the most experienced national security team in US history, he says, and look what a mess they made of things in Iraq, and what they've done for the US's good name in the world. Enough said.

Instead, Obama projects himself as fresh and new, a spokesman for a post-baby boom generation weary of the country's endless political wars, and of the hackneyed, over-hyped Blue-Red divisions.

In this vision of things, the cautious and calculating Hillary is yesterday's woman, the candidate of the status quo.

At this point, the mantle of JFK fits easily on his shoulders. In reality, President Obama would be 47 when he took office, four years older than Kennedy was on inauguration day 1961. But he projects something of Camelot's glamour and excitement, and shares Kennedy's self-deprecating charm, not to mention his stirring ability as a speaker, and ability to attract powerful supporters.

His emerging campaign team is very strong. His fundraising ability, even with the formidable Clinton machine ranged against him, is massive. If New York is lining up behind Hillary, Chicago is going with Obama, and even in Clinton-besotted Hollywood the big donors are giving the man from Illinois a very serious look. In the invisible but crucial 'money primary', he is at least holding his own.

But now the visible contest too enters a new phase. As Biden noted, Obama is "clean".

But he is not perfect. On the sin scale's trivial end, he is desperately trying to quit smoking.

More seriously, queries have been raised about a 2005 land deal with Antoin Rezko, a sleazy Chicago fundraiser, which Obama has admitted was a "bone-headed" mistake.

Charisma IF THERE are other more serious skeletons in his closet, the relentless scrutiny of a presidential race will expose them. The real questions however lie elsewhere. This talented newcomer may drip charisma from his pores. But does he have substance?

Back in 1984, former vice president Walter Mondale, the Democratic establishment's candidate for the White House, famously asked his upstart challenger Gary Hart:

"Where's the beef?" In Obama's case too it is legitimate to wonder what, if anything, lies between the two parts of the hamburger bun.

Second, is there steel to go with the charm? This election is the most open in decades, the first since 1928 in which neither a sitting president nor vice president is running. It will be a ferocious battle. Some Republicans (or was it a rival Democratic camp? ) have been falsely putting it about that the Islamic school he attended in Jakarta was a hothouse of Islamic extremism. In case you missed the point, the more childish conservative commentators roll their lips around his full name - Barack Hussein Obama, just one letter short of being an exact combination of the nation's two greatest recent enemies.

Finally, the third and most important question: can he do it? The very title of his book sets the frame for his campaign. There is audacity, to be sure. Little could be bolder and more presumptuous than for an untested 45-year old - whatever the colour of his skin - to put himself forward as saviour of the world's most powerful country, trapped in an unwinnable war, its global reputation at a nadir, when even history seems to be turning against it. The next president will be inheriting a whirlwind.

But Obama also epitomises hope. That commodity is fragile, and needs much nourishing.

Who will be your greatest enemy, he has been asked. His answer is one word: "cynicism". But for the moment Obama, more than any other candidate, offers hope.

LONG WALK TO FREEDOM: MILESTONES IN MODERN AFRICAN-AMERICAN HISTORY 1954: In the "rst major victory for the civil rights movement, Thurgood Marshall, a lawyer from the National Association for the Advancement of Coloured People, successfully argues in the Supreme Court that segregation in schools is unconstitutional.

1955: Rosa Parks, an Alabama seamstress and local rights activist, famously refuses to give up her seat in the 'coloured' section of a bus to a white man and is arrested. Her act of de"ance provokes a major escalation in the number of civil disobedience acts by blacks across the US and is widely seen as the event that sparked the civil rights movement.

1957: Eisenhower is forced to send troops to escort nine black schoolchildren from Little Rock, Arkansas, to school each day when the town's white community opposes their attendance at the former whites-only school. Despite the daily taunts they continue to attend and go on to graduate.

1962: Federal troops are sent to protect James Meredith (ABOVE), the "rst black student to attend the University of Mississippi, after major riots break out on news of his enrolment at the university.

1963: In front of a crowd of 200,000 demonstrators gathered before Capitol Hill, civil rights leader Martin Luther King Jnr (RIGHT) delivers his iconic 'I have a dream' speech, which propels the civil rights movement into the political mainstream. "I have a dream that my four children will one day live in a nation where they will not be judged by the colour of their skin but by the content of their character, " he tells the crowd.

1964: Shocked by the murder of four black girls in a Ku Klux Klan bomb and the riots that followed their deaths, President Lyndon Johnson signs the Civil Rights Act, the most sweeping racial reform legislation to date.

1965: Black empowerment leader Malcolm X, a prominent and controversial member of the civil rights movement, is shot 16 times as he delivers a speech in a New York ballroom. Three men were convicted of his murder.

1968: The civil rights movement loses its most charismatic leader when Martin Luther King is assassinated outside his hotel room by escaped convict and white supremacist James Earl Ray.

Despite promoting peaceful protest whilst alive, King's death sparks riots in more than 60 cities.

1972: Shirley Chisholm, the "rst black woman to enter Congress, adds another milestone to her CV by becoming the "rst African-American to make a bid for a presidential nomination. Chisholm says she did so "in spite of hopeless odds, to demonstrate the sheer will and refusal to accept the status quo".

1984: Reverend Jesse Jackson (RIGHT), a veteran civil rights leader and prominent Baptist minister, continues to challenge race prejudice in American politics by making numerous bids for the Democratic presidential nomination. Despite winning more than three million votes in 1984, he comes in third.

1989: At 52 years of age, Colin Powell, a highly-respected four-star general, becomes the "rst AfricanAmerican to be appointed joint chief of staff, the highest position in the US army. Powell later achieves a second race-related milestone by becoming the "rst black secretary of state under George W Bush.

1992: Some of the worst race rioting to hit the US in a decade kills 53 and tears the usually cosmopolitan city of Los Angeles apart after a predominantly white jury acquits four police of"cers of assaulting a black motorist called Rodney King. The riots provoke much soul-searching over whether race prejudice is really dead or not.

2005: Republicans break another political race boundary when Condoleezza Rice, a former professor at Stanford and longtime friend of the Bush family, becomes the "rst AfricanAmerican woman to be appointed secretary of state.