As thousands watch at Invesco Field, millions will be watching worldwide.
Obama is expected to draw from his great oratorical skills to define himself to the country. The excitement is building as the Democratic National Convention moves outside.
Invesco Field was already beginning to fill in at field-level Thursday afternoon where the Democratic delegates are seated all the way up to the nosebleed sections of the stadium.
Invesco Field has been transformed from the home stadium of the Broncos to a venue where an equally tough sport is played: politics.
Obama will be standing nearly on the 50-yard line and that may seem appropriate as he makes his play for middle America, hoping to convince the voters that are essential for achieving victory that they happen to be many of the same voters that voted for Sen. Hillary Clinton in the primaries.
The site of tonight's speech invited a new wave of Republican criticism that the White House isn't big enough for Obama's his ego.
Obama toured the stadium Wednesday night. The field has been arranged in a circular seating arrangement. And in the center, where Obama will stand, are large structures with columns that resemble the ancient Greek temple of the goddess Athena.
The grandiose setup is fueling the Republican Sen. John McCain's campaign argument that Obama is an inflated celebrity. McCain's campaign released a memo advising the press of proper attire at the "Barackopolis."
Obama's team says the move to Invesco Field is meant to open the doors of the otherwise exclusive convention to the public.
There was a lot of discussion about what Obama must do Thrusday night to create a wave of enthusiasm for his candidacy, a discussion that will continue through the next week during the Republican convention and in the short weeks that follow, leading up to election day in November.
Senator Obama said he put the finishing touches on his acceptance speech Thursday morning. He also took a break from his preparations to shoot some hoops at a Denver gym.
Security will be very tight when the first African American accepts the presidential nomination of a major political party.
The security to get in is stringent. Lines of people extended a mile long, trying to get into Mile High.
The tickets for the public were offered free. They were snapped up in about a day's time, and then they were available over the internet. Half of those went to residents of the state of Colorado. Some attendees showed up hours early.
"I didn't want to miss this. My daughter's in line because she's got a guest pass. I came because… I want to be here," said Bonnie Harris, Galesburg, Ill. "I wanted a good seat, I've got a good seat, I'm not moving for anybody."
Native Chicagoan and singer Jennifer Hudson was brought to this event by special request, none other than Obama asked her that she be the person that sings the national anthem Thursday evening. Sheryl Crow and Stevie Wonder were also slated to perform Thursday night.
After the musical acts warmed up Thursday afternoon, a series of speakers began, including Rep. Jan Schakowsky of Evanston and Congressman Louis Gutierrez from Chicago, who took the stage and hammered McCain on the topic of immigration.
"I remember when John McCain said he would stand up for immigrants until right-wing extremists told him, 'Sit down.' And sit down he did. Barack Obama will never sit down. He'll always stand up in the face of adversity for all of us in America," Gutierrez said.
Obama will likely not come to the stage until between 9 and 10 p.m., which is primetime in the Midwest and on the East Coast, where there are some important states that Obama wants to win. He wants his message to hit home in those areas.
There were tens of thousands of people waiting outside, trying to get in Yhutdfsy afternoon. The Secret Service has prohibited public parking on the lots just outside the 70,000-seat stadium, so people hae to walk long distances to get there.
The scene outside the stadium resembled a pilgrimage. Men and women of virtually every age and race moved toward a place they've been told has hope.
"It's not about race, it's not about gender, it's about making changes. We're all inheriting an incredible situation in the world today," said Mary Baum, Denver.
"I'm old enough to have been around when J.F.K. came on the scene, and I've got to tell you, I was right there, with my hand on my heart saying, 'What can I do?' And I feel exactly the same way today," said Dan Arnsmeier, Denver.
In a throwback to the pre-television era, the Obama campaign has used large crowds to highlight his oratory skills and populist appeals. On Wednesday night, he invited all of America to Invesco Field for the acceptance speech.
Secret Service police conducted individual searches of each person who entered the stadium, using x-rays and metal detectors. The searches happened after many Obama supporters waited hours in lines that, in some places, were over one mile long.
Each pass distributed there - about 80,000 of them - designated a section in Invesco Field. Attendees could sit anywhere they wanted in that section.
In Colorado, they've only elected a Democratic president three times in history. The last was Bill Clinton in 1992.
Excerpts of Senator Obama's speech were released Thursday afternoon. He'll be linking McCain to George Bush's presidency, saying McCain voted with Bush 90 percent of the time. He also plans to speak with regard to the energy state in the United States. He will say we need to harness nuclear power. When it comes to the military defense, he says, "We're the party of Roosevelt, the party of Kennedy. Don't tell me Democrats won't defend the country. He says if he becomes the president, he'll end the war in Iraq responsibly.
The democrats have been through three days of the healing process dealing with the rift between Clinton delegates and Obama supporters. With that now behind them, at least as best as can be, they can focus on the larger party goal to face off against the Republicans and their convention coming up next week.
They know from reading Obama's books and listening to his speeches that his prose is lofty, elegant and moving, but the question is, can he connect directly with the American people, can he convince people he cannot only protect American lives but make them better?
The ultimate irony of this presidential campaign is that Obama has spent little public time in Illinois or with the people of Illinois for the past 19 months because, frankly, he doesn't have to. Illinoisans know him and like him. He decided at the last minute to speak to an Illinois women's group and never notified the reporters of Chicago. But he is the favorite son of the Land of Lincoln. So delegates from Chicago and around the state are filled with pride and excitement.
"I am here because yesterday when I came, I didn't get a good seat and I wasn't going to miss this," said Harris.
Harris was the first Democratic delegate to arrive in the Illinois section of Invesco Field Thursday afternoon as thousands fought the crowds, the traffic tie ups and the security precautions en route to this historic occasion.
"This is history. I'm part of history. We're all here," Harris said.
The rest of the Illinois delegation filed in throughout the afternoon for the first outdoor acceptance speech since John F. Kennedy at the L.A. Coliseum in 1960.
"It's a historic convention, a historic time for this country. I think it's a novel idea to let everybody in," said Ashley Karamaniolas, Oswego, Ill.
Congressman Rahm Emmanuel says Obama's challenge is to connect with people like Roosevelt did in the 1930s.
"When Roosevelt was on a train from Washington to Hyde Park, a man was beside the track, like others, who was crying. A gentleman asked him, 'Did you know Roosevelt?' He said, 'No, but Roosevelt knew me,'" Emmanuel said.
Many have noted the historic nature, not merely of Obama's quest and what brought him to that very night, but also of this particular date, August 28. It was 45 years ago Thursday that Dr. Martin Luther King stood on the steps of the nation's capital in Washington, D.C. And told Americans, "I have a dream." It was 53 years ago that a young African American man, 14-year-old, Emmett Till was murdered in Mississippi. His murder galvanized the civil rights movement.
Obama's oratory skills, he admits, makes him a household name. But Thursday night, they say, don't expect high rhetoric but something down to earth. He must show voters he's a man of substance, not just style.
"He's kind of a victim of his own success… like Babe Ruth. You expect him to hit a home run every time he comes up," said Irving Rein, Northwestern University Communications Dept.
But political and communications experts say this time he must hit a grand slam. How does he do that? It won't be easy.
"We bought the emotional part, the anti-establishment part. Now tell us what you'll do," said Kenneth Janda, Northwestern univ. Political science dept..
And voters want to hear what he's going to do.
"We all know he's very charismatic," said one.
"More specific as to what this economy really needs," said another.
"I think he needs to stick with his themes. He needs to talk about the future," said another voter.
And talking specifics is exactly what the Obama campaign says the candidate is going to do.
"After tonight, people will have a true sense of who Barack Obama is," said campaign manager David Plouffe.
The campaign has characterized the speech as an intimate conversation with the American people, but how do you have one in a football stadium with 70,000 people?
"It's going to be very hard to have a direct conversation with people in a football stadium," said Janda.
Others believe Obama can pull it off.
"I think that's the perfect venue for someone like him," said Rein.
Obama's past speeches
Obama has shown an ability to connect with an audience, going all the way back four years to the last Democratic convention when he first appeared on the national stage.
Boston 2004: "My presence on this stage is pretty unlikely… There is not a black America, a white America, a Latino America, an Asian America, there is the United States of America... The hope of a skinny kid with a funny name who believes America has a place for him."
Springfield 2007: "I know I haven't spent a lot of time to learn the ways of Washington, but I have been there long enough to know that the ways of Washington must change."
Iowa 2008: They said this day would never come."
Debate, New Hampshire 2008: "While I was working on those streets watching those people lose their jobs, you were sitting on the board of Wal-Mart."
Chicago 2006: "It was a mistake, not one of my smarter moves."
Philadelphia 2008: "The church contains the cruel intelligence and the shocking ignorance, the love and, yes, the bitterness and biases that make up the black experience in America.
Minnesota 2008: After 54 hard-fought contests, our primary season has finally come to an end."
Iraq 2008: "I welcome the growing consensus in the United States and Iraq for a timeline."
Berlin 2008: "The walls between the countries with the most and those with the least cannot stand."
Denver 2008: "We want to open up this convention to make sure that everybody who wants to come can join in the party and join in the effort to take America back. I think we are going to have a great night tomorrow night and I look forward to seeing you there. God bless you. God bless America."
Jesse Jackson Jr. talks about speech
Rep. Jesse Jackson Jr. said the convention has been about introducing the Obama family to the American people and "entering their household through television an hour for Michelle, a solid hour for barack, to see who they are."
Jackson said Obama will speak to middle America, those voters who will make the final decision about the commander in chief, a voting bloc Jackson said is crucial for victory.
"The Democrat Party is too small, unless we reach out to independents and Republicans. I expect Barack Obama to do just that. He'll take this historic moment and make it a moment for all Americans. He'll reach out to that middle and bring them to the Democratic Party," Jackson said.
Jackson said exactly 45 years from Martin Luther King's "I Have a Dream" speech, "we are now to what we need to do to close the gaps in our society. Barack obama as president of the United States, working with the Congress and the Senate, has the best opportunity in the history of this nation to close the gaps that Martin Luther King Jr. was talking about. From dreaming to law making is a profound change and Barack Obama wants to lead all of us in that direction."
Jackson said he hopes the unity felt at the convention will continue on at home in Illinois.
"We saw Barack Obama and Hillary Clinton come together. If Hillary and barrack can come together, Jesse Jackson Jr. and Mayor Daley can come together," Jackson said.
The Personal Touch
Obama's unique personal story was sure to be included in his acceptance address Thursday night. Still, he also planned to talk about problems facing Americans today, from health care and education to international threats, campaign manager David Plouffe said.
"I think what Sen. Obama wants to do is make sure everyone watching at home is going to have a clear sense of where he wants to take the country, that we're on the wrong path and Barack Obama is going to put us back on the right track both here at home and overseas," Plouffe told ABC's "Good Morning America."
McCain offered mild criticism ahead of Obama's speech, saying Thursday that he admires and respects Obama but "I don't think he's right for America."
"I think I'm more in touch with the American people as far as my policies, my proposals and my ideas," McCain told KDKA NewsRadio in Pittsburgh.
Other Republicans, keeping up a theme they first used when Obama drew tens of thousands for an appearance in Berlin, derided the acceptance speech's stage as befitting a celebrity with little actual accomplishment.
"This Roman-like facade, a facade with Roman columns, is a perfect metaphor or icon for the point that it's an interesting production, but behind it there's not much there," Minnesota Republican Gov. Tim Pawlenty told ABC.
"My goodness, it's amazing that we're three days into the Democratic convention and 60 or so days from the actual election and they're still trying to plead with the American people and convince us that Barack Obama is ready to be president," said Pawlenty, who is widely thought to be a finalist for McCain's running mate. "The fact of the matter, he is not."
A modern-day technological effort was under way to get most of those packed into the stadium to form the world's largest phone bank -- text-messaging thousands more to boost voter registration for the fall.
Obama accepts his party's nod on a day few could ever imagine decades ago, when King fought for civil rights.
"This is a monumental moment in our nation's history," Martin Luther King III, the civil rights icon's oldest son, told The Associated Press on Wednesday. "And it becomes obviously an even greater moment in November if he's elected."
Obama was just 2 years old when King addressed a sea of people on the National Mall in Washington on Aug. 28, 1963. The civil rights leader proclaimed on the steps of the Lincoln Memorial, "I have a dream, that one day this nation will rise up and live out the true meaning of its creed -- 'We hold these truths to be self-evident: that all men are created equal."'
Adding a touch of celebrity to the convention's final night, singers Sheryl Crow, Stevie Wonder and will.i.am were scheduled to perform, with Academy Award-winner Jennifer Hudson singing the national anthem.
After days of suspense over whether Clinton supporters would fall in line behind Obama when the roll call of the states was called, it all fell into place in the end for Obama.
Delegates in dozens of states were allowed to apportion their votes between Obama and the former first lady before Clinton herself stepped forward to propose that Obama be declared the nominee by acclamation.
Obama himself paid a late-night visit to the Pepsi Center, home for the first three nights of the convention, where he embraced Biden and implored the delegates to help him "take back America" in the fall campaign.
"Change in America doesn't start from the top down," he told the adoring crowd, "it starts from the bottom up."
Former President Clinton did his part to bring about unity too, delivering a strong pitch for the man who outmaneuvered his wife for the nomination, and going through a litany of GOP policies the former president said were hurting the country.
"My fellow Democrats, America can do better than that. And Barack Obama will do better than that," Clinton said.
Clinton and Delaware Sen. Joe Biden, who accepted the vice presidential nomination by acclamation Wednesday night, brought Democratic jabs at McCain and President Bush into prime time as Democrats sharpened their attacks after two days of largely feel-good rhetoric.
"These times require more than a good soldier. They require a wise leader," Biden said. "A leader who can change ... the change that everybody knows we need."
Biden's attacks on McCain were a big hit among delegates eager to put aside their intraparty squabble so they can start going after Republicans.
The reconciliation was taking place, delegate by delegate.
"I was a Clinton delegate," said Darlene Ewing, a delegate from Texas. "I'm an Obama person now."
The Associated Press contributed to this report.