Democrat Barack Obama has appeared on stage to accept his nomination as the party's presidential candidate, sending a 75,000 capacity crowd wild.
After shouts of his mantra "Yes we can" finally died down, Obama formally accepted the Democratic Party's White House nomination with "profound gratitude and great humility."
Evoking King's 1963 march on Washington, Obama 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," the 47-year-old Illinois senator said as he vowed to turn back the turmoil of the past eight years and the "failed presidency of George W Bush".
And he tore into his Republican rival John McCain, saying he did not understand the struggles of normal Americans and should stop questioning his patriotism.
"It's not because John McCain doesn't care. It's because John McCain doesn't get it," Obama said.
As thousands of supporters waved tiny American flags after being whipped up into a patriotic frenzy by a pageant of patriotic songs, Obama trumpeted: "I've got news for you, John McCain, we all put our country first."
Obama also reflected on the unlikely aspects of his historic 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."
"America, we are better than these eight years," Obama said. "We are a better country than this," he said.
"We meet at one of those defining moments - a moment when our nation is at war, our economy is in turmoil, and the American promise has been threatened once more."
Obama didn't flinch from offering himself as ready not only for the title of president but also of "commander in chief".
"If John McCain wants to have a debate about who has the temperament, and judgment, to serve as the next commander in chief, that's a debate I'm ready to have," Obama said.
Melding his signature line and his rival's convention theme, Obama said the nation's troops "have not served a Red America or a Blue America - they have served the United States of America. So I've got news for you, John McCain. We all put our country first."
He vowed to end the war in Iraq and to break America's dependence on Middle Eastern oil within a decade.
Obama's energy plan would include tapping natural gas reserves, safe use of nuclear power, investments in clean coal technology and a decade-long, 150-billion-dollar program to promote "affordable, renewable sources of energy".
Obama also mocked McCain over his oft-stated pledge to capture Osama Bin Laden, accusing his rival of backing a war in Iraq that had allowed the al-Qaeda leader to escape.
In a scathing attack on his Republican foe's security policy, Obama said McCain had supported war in Iraq when the real threat to American interests remained at large in Afghanistan.
"For while Senator McCain was turning his sights to Iraq just days after 9/11, I stood up and opposed this war, knowing that it would distract us from the real threats we face."
Obama said while he had called for more troops to finish the fight against "the terrorists who actually attacked us on 9/11", McCain had sought only to "muddle through" in Afghanistan.
"John McCain likes to say that he'll follow bin Laden to the Gates of Hell - but he won't even go to the cave where he lives.
"That's not the judgment we need. That won't keep America safe. We need a president who can face the threats of the future, not keep grasping at the ideas of the past."
Obama said President George W Bush's "war on terror" had also been flawed.
"You don't defeat a terrorist network that operates in 80 countries by occupying Iraq," he said.
Obama delivered his 44-minute speech in a dramatic setting, a filled sports stadium, with camera flashes in the night, the made-for-television backdrop that suggested the White House, and the thousands of convention delegates seated around the podium in an enormous semicircle.
In addressing the convention, Obama returned to a setting where he became a national star. He was a little-known Illinois state legislator running for the US Senate when he delivered the keynote address at the 2004 Democratic National Convention.
Obama emphasised that more Americans are out of work or "working harder for less", and more have lost their homes and are falling behind on their credit card bills and school tuition payments.
He conceded that not all of the country's problems were Bush's fault but charged that the government's "failure to respond is a direct result of broken politics in Washington" and of Bush's failures.
He was confident that the country would restore its "promise" through the commitments of "ordinary men and women - students and soldiers, farmers and teachers, nurses and janitors."
Obama lashed back at Republicans who say Democrats won't defend the country, noting that World War II president Franklin Roosevelt and Cold War president John F Kennedy were Democrats.
"Don't tell me that Democrats won't defend this country," Obama 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."
He would also "restore our moral standing so that America is once more the last, best hope for all who are called to the cause of freedom".
John McCain's White House campaign dismissed Democrat Barack Obama's convention speech as "misleading" and said he was not ready to be president.