DENVER — With the burden of history on his shoulders and the expectations of more than 70,000 filling the air, Democratic presidential candidate Senator Barack Obama turned a page in American politics Thursday night (August 28) with an acceptance speech that set out to do nothing less than deliver what he called the new "American Promise."

On the 45th anniversary of Martin Luther King Jr.'s landmark "I Have a Dream" speech, Obama strode onto the stage at Denver's Invesco Field and accepted his party's nomination with a 50-minute address that was part personal history, part repudiation of the past eight years of Republican rule and mostly about a pledge to deliver on the steady mantra of his improbable 18-month rise to his party's highest calling: the promise of change.

"America, we are better than these last eight years," Obama said to thunderous applause and a sea of waving American flags and signs bearing the word "change." "We are a better country than this." He later added: "Change happens because the American people demand it — because they rise up and insist on new ideas and new leadership, a new politics for a new time. America, this is one of those moments. I believe that as hard as it will be, the change we need is coming."

Without a hint of the pressure borne of the enormity of the moment, Obama also delivered on the specifics of his plan to change America, combating the criticism that had dogged his campaign for many months — that it was more about Hollywood flash than concrete policies. He spoke about his plans for reducing taxes for most middle-class Americans, cutting the nation's addiction to foreign oil, helping college students pay for their schooling, investing in alternative energy, ending the war in Iraq and providing equal pay for equal work.

"Our government should work for us, not against us," Obama said. "It should help us, not hurt us. It should ensure opportunity, not just for those with the most money and influence, but for every American who's willing to work. That's the promise of America — the idea that we are responsible for ourselves, but that we also rise and fall as one nation; the fundamental belief that I am my brother's keeper, I am my sister's keeper.

"That's the promise we need to keep. That's the change we need right now."

Given the location, the home of football's Denver Broncos, it was fitting that the speech occasionally felt more like a Super Bowl than a political event. In addition to a succession of speeches and video packages telling Obama's story, the day was full of music, with interludes featuring everything from recordings of Motown classics by Aretha Franklin blasting over the speakers to a performance by Will.I.Am in all black and John Legend in all white, singing the Obama-boosting anthem "Yes We Can." A short time later, Sheryl Crow came out to perform a mini-set around dinnertime that included the Dalai Lama-inspired "Out of Our heads" and her venue-appropriate anthem of change "A Change Will Do You Good."

In addition, Stevie Wonder performed a few songs, and in what might have been a first at a presidential nomination acceptance speech, the boisterous crowd broke out in the wave several times before Obama began his speech and greeted a number of applause lines from the day's speakers with a thunderous stomp of the metal bleachers that likely put the dozens of snipers and lookouts posted all across the top perimeter of the stadium a bit on edge.

The bowl of the stadium slowly filled up over the course of the afternoon as the more than six-hour program capping the four-day convention ramped up to Obama's speech, with thousands of attendees waiting to enter through very tight security checkpoints in a line that snaked more than five miles long.

As he has before, Obama praised Republican rival Senator John McCain's service to America, but he said that while he couldn't claim McCain didn't care what was going on in the lives of average Americans, " I just think he doesn't know. Why else would he define middle-class as someone making under $5 million per year?" he said to a chorus of knowing nods and shame-on-you flag flicks.

"It's not because John McCain doesn't care. It's because John McCain doesn't get it." Making a plea to all Americans — red state, blue state, Democrat, Republican, independent — Obama admitted that he isn't the likeliest candidate for president. "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 naysayers don't understand is that this election has never been about me. It's been about you."

According to CNN, in a statement released after the speech, the McCain campaign called Obama's charges "misleading" and said the address was fundamentally at odds with what it called Obama's "meager record."

Referring to the white-columned structure of the stage, meant to resemble a Washington government building, McCain's statement said, "When the temple comes down, the fireworks end, and the words are over, the facts remain: Senator Obama still has no record of bipartisanship, still opposes offshore drilling, still voted to raise taxes on those making just $42,000 per year, and still voted against funds for American troops in harm's way. The fact remains: Barack Obama is still not ready to be president."

The buzz afterward inside the stadium, however, was palpable, as attendees streaming out said they felt they had witnessed a generational watershed. Kristi Detwiller, 23, of Austin, Texas, came to Denver with the College Democrats of America and said she began crying at the end of the address. "America is sinking, and he's going to be the one that lifts us back up," she said of the message she took away from the speech, which she predicted could one day have a resonance similar to King's landmark civil-rights address.

(Pete Wentz, Big Boi, Kenna and more celebs live-blogged throughout Obama's speech — check out their thoughts in the Newsroom blog.)

For Albuquerque, New Mexico, native Vanessa Nielsen, 29, who was carrying an infant on her chest as her dreadlocked husband pushed their toddler in a stroller, Obama's words were worth the trip. "And we're worth that. Ultimately, this isn't about Barack. It is so much about our future and what we're going to do. I'm so impassioned right now. He really is for the people, and that's why people are feeling so excited. I've never been so excited about a candidate before."

As the cheers grew to a din and the audience rose to its feet and swung their flags and placards, Obama's voice rose with the lines "America, we cannot turn back. Not with so much work to be done. Not with so many children to educate and so many veterans to care for. ... America, we cannot turn back. We cannot walk alone. At this moment, in this election, we must pledge once more to march into the future. Let us keep that promise — that American promise — and in the words of scripture, hold firmly, without wavering, to hope that we confess."

The evening ended with a blast of red, white and blue fireworks from the stadium's rafters, patriotic streamers and confetti raining down and whoops of "yes we can" from the crowd as Obama's family mingled with that of his vice-presidential pick, Senator Joe Biden.

"Nobody has every seen something like this before," said Camille Rivera, 29, who came from the Bronx, New York, to see the speech. "From Martin Luther King's speech to where we are now, who would have ever thought that a person of color would be sitting at the doorsteps of the White House to become president of the United States?"