Today a magic spell will be performed. A man who 12 weeks ago was a mere political candidate will be transformed with the incantation of a few words, before a vast crowd and a television audience in the hundreds of millions if not billions, into the head of state, even the embodiment, of the most powerful nation on earth.  It is an act of political alchemy that happens every time a new president is inaugurated, but rarely has the moment been as anticipated as this one. Washington DC, usually a city of strait-laced, sober-suited types has acquired the atmosphere of a child's bedroom in the first hours of Christmas morning. There are snow flurries outside, tacky decorations everywhere - and the resolve to wake up early, so as not to miss a moment of the great day. The excitement is intense and has been building for days, increasing with each coachload of newcomers that arrives in the city. Women wear woolly hats against the cold, the word OBAMA spelled out in diamante letters. Street-hawkers sell T-shirts bearing Obama's face, alongside ever more grandiose slogans. One shows a beatific president-to-be under the quasi-biblical declaration: "And he shall be called Barack Obama." The street merchandise, the nightly parties, the rare sighting of Hollywood A-listers among the policy wonks and thinktankers - that happens every four years. But no one would deny the extra fervour this time. The most obvious explanation is written on the faces of African-Americans who have travelled so far to be here. "This moment won't come again," said Robert Davis, 63, who had travelled from Cincinnati, Ohio. "There may be another black American president, but this will always be the first time."  He was part of the throng at the Lincoln Memorial yesterday, destination for many of those who have come to see Barack Obama sworn in. Perhaps it was a way to place their desire to witness history in a historical context - close to the monument to the president who ended slavery, the site where Martin Luther King declared his dream of equality. In this, the fates have once again helped endow Obama's inauguration with an epic quality. He accepted the Democratic party's presidential nomination on the 45th anniversary, to the day, of the "I have a dream" speech. Yesterday, the day before Obama's installation as president, was Martin Luther King day. It added to the sense that America will today reach some kind of fulfilment, even redemption. "King's dream became a reality," said Davis, his voice wavering in the cold. But it is not only black America's pride in Obama that is lending extra magic to today's act of sorcery. For one thing, there is the sheer eagerness to see the back of the present incumbent, George W Bush, who marked a "mostly private" last day in office yesterday by granting a cluster of pardons and making a series of goodbye calls to world leaders. No president has left office with lower approval ratings. For another, it is the fact that today's inauguration ceremony will not need to deploy too much magical power to persuade Americans to see Barack Obama as their president. Proof of that is palpable in his dizzyingly high poll ratings, with 79% optimistic about the next four years, according to the New York Times, a degree of goodwill that trumps the numbers that greeted the previous five presidents. The same poll found high levels of hope among those who voted for Obama's opponent, John McCain. It's partly because he has, in the three months of transition, done much to reassure them, appointing solid, centrist figures, including more than one Republican, to key positions. Last night he was due to attend three private dinners honouring the public service of his vice-president-to-be, Joe Biden, and Republicans Colin Powell and McCain himself. But it's also because the new president does seem blessed with the poise and stature that befits a head of state. Yesterday he again looked the part, visiting wounded soldiers at the Walter Reed army medical centre, then rolling up his sleeves and helping paint the walls at a homeless shelter for teenagers in north-east Washington - with Martin Luther King's son at his side. Obama had urged his vast email database of supporters to follow his lead and engage in a day of community service. Among those heeding the call was Michelle Obama who, with her daughters, went to Washington's RFK stadium to join 15,000 volunteers in assembling "care packages" for US soldiers serving abroad.  But, in a visit to the Calvin Coolidge high school, Obama said that this could not be a "one-day affair". He added: "If we're waiting for someone else to do something, it never gets done." That prefigures what is set to be one of Obama's major themes today: responsibility, the notion that government cannot solve America's vast problems alone, that everyone has to pitch in. That fits nicely with Obama's insistence that he will be able to work no miracles as president; that tackling the deepening economic crisis will be the stuff of long, hard work. The polls suggest Americans understand that. They know there will be no overnight fix. And they applaud their incoming president for saying so. Indeed, his caution and realism only make them admire him more.  Such are the paradoxes of a man who insists he is no magician - but who will stand today at the centre of something magical.