Following a dramatic appearance by Hillary Clinton on the packed floor of the Democratic Convention, Barack Obama, the Hawaiian-born son of a mother from Kansas and a father from Kenya, was finally and officially named the party's presidential candidate last night.

Mrs Clinton swept on to the convention floor just as her home state, New York, was being called upon to cast its vote during a raucous roll-call of the delegates of all states. In a striking gesture of unity after all the months of bitterness, Mrs Clinton took the microphone to formally ask that the vote be suspended and that the convention approve the Obama nomination by acclamation.

"With eyes firmly fixed on the future, in the spirit of unity... let's declare together in one voice, right here right now, that Barack Obama is our candidate and he will be our president," she said, reading from a script.

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"I move Senator Barack Obama of Illinois be selected by the convention by acclamation as the nominee of the Democratic Party" she added, lifting the roof of the convention hall. Her request was instantly accepted by Nancy Pelosi, the convention's presiding officer.

Mrs Pelosi then announced that Barack Obama had accepted the nomination.

The stage is now set for Denver's vast outdoor arena where tonight, on the 45th anniversary of Martin Luther King's "I Have a Dream" speech, Mr Obama will deliver an address upon which hangs the outcome of November's American presidential election, and the hopes of the first black man with a real shot at the White House.

Eight years ago, such a scenario would have been laughable. Obama was broke and without political friends of any consequence. He had to gatecrash the 2000 Democratic Convention in Los Angeles after arriving on a cheap flight at the last minute. A rental car company rejected his maxed-out American Express card and he watched Al Gore accept the party's nomination on television screens at the perimeter of the convention centre.

Tonight will seem a millennium away. This time, it will be Gore in the audience lending support to the candidate on whose slender shoulders the Democrats' hopes lie. The psychodramas surrounding Hillary Clinton have also been dealt with following the rapturous reception for her barnstorming speech to the convention on Tuesday.

Senator Obama's acceptance of the nomination before 70,000 people is set to be an extraordinary political event. The task at hand is to energise the party and reconnect Obama's "colourblind" vision for the country with those Republicans who were briefly enthralled by his electrifying promise to unify America's angry and divided politics.

Back in 2000, at the age of 39 and with his career crashing around him, his hopes seemed to have flamed out after he had been trounced while trying to unseat a well-liked black Congressman. He recalls being terrified that for all his dreams he was about to disappear from public life – just as his talented Kenyan father had done before him.

Last night, he arrived in Denver on a private Boeing 757 with his name emblazoned on the side. It was yet another giant step in the remarkable journey from ambitious local politician to global political superstar, who may from January be President of the world's troubled superpower.

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Tonight, millions of Americans – and millions more around the world – will hang on his every word. But John McCain, whose campaign is ratcheting up the attacks on Obama's inexperience with every hour, will be watching too. Even Obama's decision to choose the experienced political warhorse Joe Biden as his running mate has not given him the hoped-for "bounce" in the polls.

Yet, during the past eight years, it is Obama's extraordinary ability to rise to the occasion that has marked him out from the crowd. Campaigning this week in four battleground states – Wisconsin, Iowa, Missouri and Montana – he has worked late into the night with a pen and yellow pad, crafting in longhand what is expected to be the speech of his lifetime.

Mr Obama has given hundreds of stump speeches over the past two years, some of them inspiring, many of them repetitious. But it is an address delivered in 2002 to a group of war protesters in which he flatly stated his opposition to the invasion of Iraq that he considers his best.

Just a year after 11 September 2001, with Mr Bush riding high and polls supporting an invasion – and just as he was preparing to run for the US Senate – he committed what many thought to be political suicide.

"I don't oppose all wars," he said. "What I am opposed to is... a war based not on reason, but on passion, not on principle but on politics." That seemingly foolhardy, if prescient, statement made him the only top-tier presidential candidate flatly to oppose the war before it was launched. Until 2004, he languished in the backwaters of Chicago, an obscure state senator – the lowest form of pond life in national politics. Then he was noticed by John Kerry, the Democratic candidate of that election year. Wooden and uninspiring, Kerry was on the lookout for a talented black politician. After seeing Obama skilfully work a room of white voters, he soon invited him to deliver the keynote address at the 2004 Democratic National Convention in Boston.

It was just 17 minutes long but the speech captured America's attention. The speech, which Obama insisted on writing himself, was hailed as a classic by the political world and earned him comparisons to John F Kennedy and Martin Luther King.

It has become part of the myth of Obama's effortless rise as a political phenomenon. But behind the legend lies a cunning, an extraordinary ambition and an unrivalled attention to detail that he learnt going door to door as a community organiser in Chicago's South Side.

That trademark micro-management was in evidence again yesterday as his campaign succeeded in short cutting the roll-call of states – thereby avoiding the embarrassment of the biggest states declaring for Hillary Clinton. The Obama camp ensured that long before most Americans switched on their TVs last night – Barack Obama was already the Democratic nominee to become the 44th US president.

King's dream and the road to Denver

1870: Hiram Revels, a Republican from Mississippi, is the first African American elected to the US Senate.

1954: Thurgood Marshall, a lawyer for the National Association for the Advancement of Coloured People (NAACP), successfully argues for the end of school segregation before the US Supreme Court. In 1967, he becomes the first African American to serve on the court.

1955: Rosa Parks, a seamstress and civil rights activist in Alabama, refuses to give up her seat on a bus to a white person. Her act propels the Civil Rights movement forward.

1963: Martin Luther King, pictured, leads the March on Washington for Jobs and Freedom that brings 250,000 to the capital on 28 August – 45 years ago. The event culminates with his "I Have a Dream" speech from the Lincoln Memorial. (King is assassinated in April 1968.)

1968: Shirley Chisholm becomes the first African-American woman elected to the US Congress. In 1972, she runs for the Democratic presidential nomination.

1984: The Rev Jesse Jackson makes the first viable bid by an African American for his party's presidential nomination. He wins more than three million votes in the primaries, but eventually comes third.

2001: Colin Powell, a four-star general, is chosen by George Bush as Secretary of State, the first time an African American has served in that position. He was also the first black Chairman of the Joint Chiefs of Staff, the highest military rank in the US, in 1999.

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