US Democratic presidential candidate Barack Obama savaged John McCain and 'broken' Republican politics before a crowd of 75,000 supporters in Denver, Colorado.
The final night of his party's convention was moved from a basketball arena to an American football stadium next door and opened up admission to the general public.
It was the first time any Democratic presidential nominee had done so since John F Kennedy in 1960 - and took place on the 45th anniversary of Martin Luther King's 'I Have A Dream' speech.
Senator Obama cited Dr King during his speech, but not before he attacked his opponent.
‘America, we are better than these last eight years,’ Senator Obama said. ‘We are a better country than this.'
Mixing poetry with policy and handcuffing John McCain to President George W Bush, he added: 'This moment, this election, is our chance to keep in the 21st century the American promise alive.'
‘We are here because we love this country too much, to let the next four years look like the last eight. On November 4, we must stand up and say 'eight is enough'.'
Senator Obama held the massive crowd crammed into the open-air football stadium enthralled as he swept through his speech, punctuated by multiple standing ovations.
A barrage of multi-coloured fireworks and blizzard of confetti filled the Rocky Mountain skies when he finished.
Hitting new heights just four years after exploding onto the US political scene, Barack Obama gave notice he would fight back hard at a sustained volley of Republican assaults on his capabilities and patriotism.
He said John McCain did not understand the struggles of working Americans, as they see their jobs disappear abroad, living expenses rise, and prospects dim.
‘It's not because John McCain doesn't care. It's because John McCain doesn't get it,’ he said.
As thousands of supporters waved tiny US flags after being whipped into a frenzy by a pageant of patriotic songs, Mr Obama trumpeted: ‘I've got news for you, John McCain, we all put our country first.’
He furiously rebutted Republican claims ahead of the party's convention next week that he was too inexperienced to be US commander-in-chief.
‘Don't tell me that Democrats won't keep us safe,’ he said.
‘The Bush-McCain foreign policy has squandered the legacy that generations of Americans - Democrats and Republicans - have built and we are to restore that legacy.’
Mr Obama gave detailed policy prescriptions of what he would do as president, in the knowledge that many US citizens may have been tuning into his campaign for the first time.
He castigated President Bush and Mr McCain for bad judgement, saying his White House foe would not end the ‘misguided’ war in Iraq, and would make the US less safe with hawkish foreign policy.
‘If John McCain wants to follow George Bush with more tough talk and bad strategy, that is his choice - but it's not the change we need.’
At home, Mr Obama promised to stop tax breaks for the rich, and cut taxes for the middle class, and said he would break America's dependence on foreign oil in 10 years, and give every child a 'world class education.’
Evoking Martin Luther King Jr’s 1963 March on Washington speech, the Illinois senator said what ‘people of every creed and colour, from every walk of life’ heard ‘is that in America, our destiny is inextricably linked, that together our dreams can be one.’
‘America, we cannot turn back.’
Mr McCain's campaign swiftly dismissed Senator Obama's speech.
‘Tonight, Americans witnessed a misleading speech that was so fundamentally at odds with the meagre record of Barack Obama,’ said Mr McCain spokesman Tucker Bounds in a statement. ‘The fact remains, Barack Obama is still not ready to be president.’
Leaning heavily on his biography, as the mixed race son of a broken home, Mr Obama also sought to address the unlikely aspects of his audacious White House quest.
‘I get it, I realise that I am not the likeliest candidate for this office,’ he said. ‘I don't fit the typical pedigree, and I haven't spent my career in the halls of Washington.
‘But I stand before you tonight because all across America, something is stirring. What the nay-sayers don't understand is that this election has never been about me, it's been about you.’
Meanwhile, US media reported this afternoon that John McCain has chosen Alaska Governor Sarah Palin as his vice presidential running mate.
Mr McCain and the Republicans begin their convention on Monday in St Paul, Minnesota.
Check out complete convention coverage including our photo gallery and full text of speeches at RTÉ.ie/uselection
