Barack Obama made a surprise appearance Wednesday at the Democratic National Convention, but it was just a warm up for the history making moment that awaits him tonight when he becomes the first black man to accept the presidential nomination of a major political party.
Obama will claim the nomination tonight before a crowd so large the convention will be moved to a 70,000 seat sports stadium, Invesco Field. Adding poignancy to his remarkable moment, he will become the party's leader on the 45th anniversary of Martin Luther King Jr.'s "I Have a Dream Speech."
The Democrats' new leader popped out of the wings Wednesday night after a rousing speech by his vice presidential candidate, Joe Biden.
As delegates roared inside the Pepsi Center in Denver, Obama referred to a speech by his wife on Monday: "I think Michelle Obama kicked it off pretty well, don't you think?" he said.
Michelle Obama mouthed, "I love you," from her skybox seat.
"If I'm not mistaken, Hillary Clinton rocked the house down last night!" Obama said, referring to his chief rival for the Democratic nomination, who addressed the convention Tuesday.
Obama even offered praise for Bill Clinton, who had been aggressive toward Obama on the campaign trail, but enthusiastically endorsed of the Democratic nominee before the convention crowd earlier Wednesday.
Obama called Clinton "someone who reminds us what it's like when you've got a president who actually puts people first. Thank you, President Clinton."
A night that could have been all about former President Clinton's speech now also will be remembered for Obama's appearance.
Obama walked out onto the stage after Biden praised his Democratic ticket mate and delivered an aggressive attack on their Republican rival, John McCain.
Watch Charlie Gibson, Diane Sawyer and George Stephanopoulos at the Democratic Convention TONIGHT at 10 p.m. ET on ABC.
Democrats earlier made Obama's nomination official when party delegates formally picked him as their 2008 presidential candidate, making Obama the first African-American ever nominated by a major party.
Obama was at a Denver hotel with his wife, Michelle, and his daughters Malia, 10, and Sasha, 7, and extended family when he learned that he was officially the nominee.
A woman delegate was seen weeping as Obama's primary rival Sen. Hillary Clinton moved to nominate Obama by acclamation.
Obama's campaign manager David Plouffe said the candidate was moved by the moment.
"Even though we became the presumptive nominee some time ago, it became reality last night. And to see Sen. Clinton be so gracious in moving our nomination by acclamation, and really to see the eruption in the hall and the sheer sense of joy and excitement about the election was really a special moment," Plouffe told "Good Morning America."
Hollywood stars and musicians were in the audience as history was made. Director Steven Speilberg and his wife Kate Capshaw sat in a skybox. Musician Melissa Etheridge performed "God Bless America."
Biden was formally nominated as the party's vice presidential candidate Wednesday, as well. His nomination was seconded by his son, Beau, as more than two dozen additional family members joined them in the convention hall, including Biden's 92-year-old mother, Jean.
An emotional high point came when Beau -- Delaware's attorney general, who is deploying to Iraq in October -- described the days after a car crash killed his mother and sister.
"One of my earliest memories was being in that hospital, Dad always at our side," Beau Biden said. "We, not the Senate, were all he cared about. He decided not to take the oath of office. He said, 'Delaware can get another senator, but my boys can't get another father.' However, great men like Ted Kennedy, Mike Mansfield, Hubert Humphrey -- men who had been tested themselves -- convinced him to serve."
Tears rolling down her face, Michelle Obama dabbed her eyes with a tissue throughout Beau and Joe Biden's speeches.
Members of the crowd were on their feet cheering when Biden took the stage and said, "Yes, yes, I accept your nomination!"
He reminded voters of his working class background in Scranton, Pa., and Wilmington, Del.
"Barack Obama and I took very different journeys to this destination, but we share a common story," he said. "Mine began in Scranton, Pa., and then Wilmington, Del., with a dad who fell on hard economic times, but who always told me, 'Champ, when you get knocked down, get up. Get up.'"
Biden told how his mother helped him through a stuttering problem as a child.
"My mother's creed is America's creed: No one is better than you. You are everyone's equal, and everyone is equal to you," Biden said.
Then Biden launched into an aggressive assault on McCain, playing the attack role of vice presidential candidates in the past.
"Almost every night, I take the train home to Wilmington, sometimes very late," Biden said. "As I look out the window at the homes we pass, I can almost hear what they're talking about at the kitchen table after they put the kids to bed."
Biden said millions of Americans are asking questions about their economic security.
"That's the America that George Bush has left us, and that's the future George, excuse me, John McCain ... will give us -- Freudian slip! Freudian slip," he said.
"As we gather here tonight, our country is less secure and more isolated than at any time in recent history," he said. "The Bush-McCain foreign policy has dug us into a very deep hole with very few friends to help us climb out."
Contrasting Obama and McCain on foreign policy, Biden said, "The choice in this election is clear. These times require more than a good soldier; they require a wise leader, a leader who can deliver change -- the change everybody knows we need. Barack Obama will deliver that change."
"Now, after six long years, the Bush administration and the Iraqi government are on the verge of setting a date to bring our troops home," Biden said, "John McCain was wrong. Barack Obama was right."
"This is his time, this is our time," Biden added. "God bless America and protect our troops!"
While all the party unity stagecraft was carefully planned, it was a speech tonight by former President Bill Clinton that threatened to remind voters of just how divided the party was during the bitter and lengthy primary campaign.
When the former president walked on stage Wednesday night, the crowd erupted into such wild applause that he asked them to stop.
"I love this, but we have important work to do tonight," he said after basking in the glow of the applause.
"First of all," he said, "I am honored to be here tonight to support Barack Obama."
Clinton added, "And to warm up the crowd for Joe Biden -- though as you'll soon see, he doesn't need any help from me. I love Joe Biden, and America will too."
Praising his wife, Clinton said the party's primary began with an "all-star line up and came down to two remarkable Americans locked in a hard-fought contest to the very end."
"In the end, my candidate didn't win," he said. "But I'm very proud of the campaign she ran: She never quit on the people she stood up for, on the changes she pushed for, on the future she wants for all our children. And I'm grateful for the chance Chelsea and I had to tell Americans about the person we know and love."
"Hillary told us in no uncertain terms that she'll do everything she can to elect Barack Obama," the former president said. "That makes two of us. Actually that makes 18 million of us -- because, like Hillary, I want all of you who supported her to vote for Barack Obama in November."
At one point in his speech, as the crowd cheered Obama's campaign refrain, "Yes we can! Yes we can!" Clinton ad-libbed, "Yes he can, but first you need to vote for him."
As of late afternoon, the two-term president had not finished his speech, and senior Obama campaign officials told ABC News that neither Obama nor anyone from the campaign had seen it.
That's rare. Even Hillary Clinton, Obama's closest primary rival, ran her speech by the Obama campaign before delivering it.
While Obama campaign officials said they weren't nervous about Bill Clinton's speech Wednesday, there may have been good reason to be nervous after a bitter primary battle in which the former president aggressively went after Obama in support of his wife's candidacy.
There are are perceived tensions between the man who will become the nation's first major party African-American presidential candidate, and the man who was once dubbed America's "first black president."
However, Bill Clinton said all the right words. Watching from the stands and rising to applaud him was potential first lady Michelle Obama, who sat beside Theresa Heinz Kerry, wife of 2004 Democratic presidential candidate John Kerry.
"Barack Obama is ready to lead America and restore American leadership in the world," Clinton told the cheering crowd. "Barack Obama is ready to honor the oath to preserve, protect and defend the Constitution of the United States. Barack Obama is ready to be president of the United States."
The former president was given a less desirable speaking slot Wednesday, addressing the crowd ahead of Kerry and New Mexico Gov. Bill Richardson, and not during the prime time hours that the major networks will carry the events. Richardson was eventually bumped from the Wednesday night program because they ran out of time, but will now speak Thursday night.
While Bill Clinton is the only Democrat elected to a second term in the White House since Franklin Delano Roosevelt, received much criticism from his own party during the extended primary battle. He created an uproar after a South Carolina Democratic primary that prompted anger among some in the African-American community.
After Obama defeated his wife there, the former president seemed to downplay the significance of the victory by noting Jesse Jackson had won South Carolina in 1984 and 1988, even though Jackson did not go on to win the overall contest -- a comparison some observers found offensive.
The controversy later brought an apology from Hillary Clinton, who told reporters, "You know, I am sorry if anyone was offended. It was certainly not meant in any way to be offensive."
"I am not a racist," Bill Clinton told ABC News' Kate Snow earlier this summer . "I've never made a racist comment and I never attacked him [Obama] personally."
When asked whether he thought Obama was ready to be president, the former president offered only a tepid answer.
"You could say that no one's ever really prepared to be president," he said.
Some African-American Democrats said going into Wednesday's speech that kind of endorsement wasn't going to be enough.
Democratic convention volunteer Christine Easterling, 59, of Silver Spring, Md., a retired educator, said Clinton has some work to do to show he supports Obama.
"His comments were racist," she said. "But if he knew how to make it bad, then he knows how to make it right again."
Outside the convention hall today, volunteering with his wife for the convention's "green team," Spence Havlick, 73, a University of Colorado city planning and architecture professor, said he wishes Clinton would go back to playing the role of elder statesman.
"We've always been very impressed with him, and I just wish he would continue to be an elder statesman, like a younger Jimmy Carter," he said.
But some of the bitterness of the primary lingered in the convention hall before the main speeches Wednesday. Some attendees still expressed disappointment that Hillary Clinton wouldn't be the Democratic Party's official presidential nominee.
"I still feel like I lost something," Peggy Tanksley, a Clinton delegate from Ohio.
"I remember going through each and every one of those primaries thinking this one is going to push her over," she said. "No it's not, this one is going to push her over. ... No it's not. And so I think it was a continual process of being excited and anxious and let down ... excited, anxious, and let down."
The traditional state-by-state roll call went on until about 6:40 p.m. ET, just after the network newscasts had gone on the air on the East Coast.
The roll call included several delegates cast to Clinton, whose name was formally put into nomination even though she did not win the primary battle.
By previous agreement between the Obama and Clinton camps, the roll call was halted and Obama was nominated by acclamation.
Midway through the alphabetical roll call, New Mexico yielded the floor to Illinois, which had passed its turn previously so that the candidate's home state could be the final one to cast its vote. Illinois, represented by Chicago Mayor Bill Daley, then yielded to the state of New York "home of Hillary Clinton."
And finally, the junior senator of New York, representing her state, moved to declare Obama the party nominee.
"I move that the convention suspend the procedural rules and suspend the further conduct of the roll call vote, [that] all votes cast by the delegates will be counted, and that I move that Sen. Barack Obama of Illinois be selected by this convention by acclamation as the nominee of the Democratic Party for president of the United States," Clinton said.
Earlier, Clinton officially "released" her delegates, clearing them to back Obama during the roll call vote. She did not tell them to do so formally, although she did just that informally in her speech before the convention Tuesday night.
"I am here today to release you as my delegates," she said. Loud boos were heard in the room, presumably from Clinton loyalists.
She added, to cheers, "I am not telling you what to do."
Clinton said she herself marked her ballot for Obama Wednesday morning.
"Many other people who sign their ballots will make a different choice," she said. "You are to be given the respect and recognition you have earned as delegates for the Democratic Party."
With the theme Wednesday of "Securing America's Future," many of the Democratic heavyweights who spoke at the convention touted Obama as ready to lead the country in a time of war.
Republicans have stepped up their efforts to paint Obama as an inexperienced celebrity who is "not ready to lead." And the message may be working: The latest ABC News/Washington Post poll showed McCain leading Obama by 2-1 margins as more knowledgeable on world affairs and as better-suited to be commander in chief.
Trying to reverse that, Bill Clinton argued the country needs Obama's ability to inspire people around the world.
"Clearly, the job of the next president is to rebuild the American dream and restore America's standing in the world," he said. "Everything I learned in my eight years as president and in the work I've done since, in America and across the globe, has convinced me that Barack Obama is the man for this job."
Massachusetts Sen. John Kerry, who was attacked by Republicans as a "flip-flopper" when he was the Democratic presidential candidate in 2004, issued a blistering attack on John McCain's positions and judgment on foreign policy and national security.
"Candidate McCain now supports the wartime tax cuts that Sen. McCain once denounced as immoral," Kerry said. "Candidate McCain criticizes Sen. McCain's own climate change bill. Candidate McCain says he would now vote against the immigration bill that Sen. McCain wrote. Are you kidding? Talk about being for it before you're against it.
"Let me tell you, before he ever debates Barack Obama," Kerry added, "John McCain should finish the debate with himself."
Former Secretary of State Madeleine Albright asked why Americans should trust Republicans to safeguard the nation's security.
"We cannot afford four more years like the past eight years -- policies that embolden our enemies, undermine our economy, and place an unfair burden on the heroes of our armed forces," she said. "John McCain asks that we trust Republicans to safeguard our national security -- to which we can only reply: Why would we?
"We need a president who is not wedded to 20th century thinking, who can forge a network of power and principle that will keep America strong and safe in the 21st century," she said.
ABC News' Kate Snow, Matt Jaffe, Jake Tapper, Karen Travers, Teddy Davis, Tahman Bradley, Eloise Harper, Sunlen Miller, and Rick Klein contributed to this report.