The focus of the campaign now moves to Wisconsin, and to Hawaii where Mr Obama was born to a Kenyan father and a white mother 46 years ago. The media frenzy surrounding his race for the White House is now such that anything less than a crushing defeat of his opponent in these contests next Tuesday will be viewed as a stumble.
Yesterday Mr Obama received another boost when Bill Clinton's campaign chairman from 1992 endorsed him. David Wilhem is sased in Wisconsin and is a so called 'super-delegate''s so his backing is more than symbolic. Mr Obama meanwhile condemned attacked Mrs Clinton and the republicans over the economy saying, "we are not standing on the brink of recession due to forces beyond our control," but that "It was a failure of leadership and imagination in Washington - the culmination of decades of decisions that were made or put off without regard to the realities of a global economy."
By overwhelming Mrs Clinton on Tuesday in Virginia, Maryland and Washington DC, the so-called Potomac primaries, Mr Obama captured impressive support from every group of voters. In winning the backing of women, he removed one of the last important bulwarks propping up the Clinton campaign. Mr Obama won 75 per cent of the vote in Washington, DC, and nearly two-thirds in Virginia. In Maryland, he took almost 60 per cent of the vote.
All day yesterday, political commentators bubbled over with praise for the Obama campaign, noting that he has tapped into an insistent popular demand for change in Washington. His call for wholesale change in the way Washington politicians are funded by and do deals with industry lobbyists and insiders has resonated with Americans facing growing unemployment, falling incomes and an insecure economic future. They support his demands for a change far more profound than merely finding a Democratic Party replacement for the unpopular George Bush.
Senator Clinton has been telling voters she has 35 years of experience in government and is "tested and ready" to step into George Bush's shoes. The problem, said the political pundit Chris Matthews, "is that nobody wants a replacement for George Bush, they don't want the president to look like that any more".
In Mr Obama's victory speech before 18,000 cheering supporters in Madison, Wisconsin, he took the battle to the "Bush-McCain Republicans", acting as if he had already won enough delegates to be Democratic nominee in November.
Senator John McCain also had a three-contest sweep against his opponent Mike Huckabee and Mr Obama is already behaving as if a McCain-Obama match-up in November is now inevitable.
"John McCain is an American hero," Mr Obama told a cheering crowd, acknowledging his opponent's five long years of torture and imprisonment in a North Vietnamese jail. "We honour his service to our nation. But his priorities don't address the real problems of the American people, because they are bound to the failed policies of the past."
Mr McCain quickly struck back, telling a victory rally in Virginia that rather than offer "sound and proven ideas that trust in the strength and courage of free people", Mr Obama offered "not a promise of hope, [but] a platitude".
"My friends," Mr McCain said, stealing one of Mr Obama's campaign refrains, "I promise you, I am fired up and ready to go." But the challenge the 71-year-old Mr McCain faces was evident from the elderly supporters surrounding him. "They looked as if they had been rounded up at a nearby hospice," said the irascible Pat Buchanan, a former republican presidential candidate turned TV pundit.
By contrast, Mr Obama's victory rally in Wisconsin saw him surrounded by a sea of multiracial supporters waving banners and cheering his now-familiar punch-lines.
Mrs Clinton was meanwhile in El Paso, Texas, trying to shore up the support of Hispanic voters and not even mentioning in her speech the trouncing she had just received in the Potomac primaries. Mrs Clinton gave her speech everything she could and it was carried live on several television channels. But a tin ear combined with a hectoring voice and a tendency to drone on about herself left audiences uninspired.
Mr Obama has a huge advantage over Mrs Clinton in the final stages of the race for the nomination. He has reversed what seemed to be her unassailable lead in the national polls. He has a war chest of tens of millions of dollars and is already blitzing states like Wisconsin, Texas and Ohio with soft-focus ads that show him in presidential light. Although Mrs Clinton may have denied him victory in the large delegate-rich states of California, New York and New Jersey, he has won more races overall.
Mr Obama is also ahead in the crucial head-count of delegates pledged to him for the nominating conference in late August. A majority of hand-picked "super-delegates" still favour Mrs Clinton. But these party hacks and politicos are expected to transfer to Mr Obama's side "like birds on a wire" if it becomes clear that he has overwhelming popular support in the party.
That will probably have to wait until the next big test in the primary season on 4 March when Texas and Ohio vote.
Mr Obama now has 1,223 delegates including superdelegates. Mrs Clinton has 1,198 and has fallen behind for the first time since the campaign began. Neither candidate is near to the 2,025 needed to win the nomination.
© 2008 The Independent