BARACK Obama put meat on the bones of his promise of "change" with a tub-thumping speech at Denver's Invesco Field football stadium on Thursday – but only the polls will show if voters believe that he can deliver.
Mr Obama's key weakness in the United States presidential election campaign has been the perception that he is all rhetoric and no substance.
So amid the fireworks, pounding music and roars of an electrified 84,000 crowd, the Democrat candidate
attacked the criticism head on: "Let me spell out exactly what change would mean if I am president." Top of his list was tax cuts for the middle-class, to be paid for by the rich, plus protectionist trade measures to stop the flow of jobs overseas.
There were traditional liberal promises of more money for education and health, plus a $150 billion (£82 billion) investment in renewable energy. And on foreign policy he repeated pledges to withdraw from Iraq and a new engagement with allies.
These promises fit into a narrative that sees America as having been driven into the ditch by eight years of failures and cronyism by the Bush administration, supported by John McCain, his Republican rival.
"For over two decades (Mr McCain has] subscribed to that old, discredited Republican philosophy: give more and more to those with the most and hope that prosperity trickles down to everyone else," Mr Obama said.
"What it really means is that you're on your own. Out of work? Tough luck. You're on your own. No healthcare? The market will fix it. You're on your own."
Instead, Mr Obama sought to cast himself as following the legacy of John F Kennedy, the last presidential candidate to give an election speech in a stadium, and Martin Luther King, whose "I have a dream" speech came 45 years ago to the day. "What has been lost these past eight years can't just be measured by lost wages or bigger trade deficits," Mr Obama said. "What has also been lost is our sense of common purpose."
He insisted this common purpose included not just compassion, but also Republican values of self-reliance and a level playing field: "Individual responsibility and mutual responsibility – that's the essence of America's promise," he said.
All of this was coupled with his most robust attack on his rival: "The record's clear: John McCain has voted with George Bush 90 per cent of the time," he said. "I don't know about you, but I'm not ready to take a 10 per cent chance on change."
There was a nod also to foreign policy, with a pledge to hunt down Osama Bin Laden coupled with a call to end the go-it-alone stance of the Bush administration that Mr Obama says has crippled foreign policy: "You can't truly stand up for Georgia when you've strained our oldest alliances."
But for many voters, the doubts about whether this fresh-faced senator can deliver are likely to remain. His promise to raise spending and cut taxes in a country heading into recession will have economists scratching their heads.
Anxious lest he be portrayed as a tax-and-spend liberal, Mr Obama insists that he will "pay for every dime" through ending tax breaks and wasteful spending. Not everyone will agree that the numbers add up.
Supporters in the stadium were, however, enthused: "It was the best speech I've heard him make," said Bob Levine, a party official from Missouri. This will be a big help to Mr Obama in the weeks ahead.
Election success in November will depend on his ability to convince the famously lethargic younger voters to make it to the ballot box – traditionally many don't bother.
But the true test of the speech will have to wait. Not for the rush of opinion polls this weekend, which give him a post-convention "bounce", but for the end of next week's Republican convention, when Mr McCain can expect his own surge in support.
Only when the dust settles on both conventions do the polls mean anything. Going into his convention, Mr Obama was neck and neck with Mr McCain, having been in front earlier.
Some supporters worry that Mr Obama has raised expectations to the point where, should he become president, disappointment is inevitable. "If he makes it to the White House, he'll have an enormous mess to clean up. If it doesn't go as smoothly as we'd like to see, then critics will say 'I told you so'," said Eric Hardin, a Denver resident.
