The Republican presidential nominee-to-be and his newly minted running mate were to make a midday appearance at a rally in swing-state Ohio and continue to rallies in Pennsylvania and Missouri in the run-up to the Republican National Convention, which starts Monday in St. Paul, Minn.
Obama was flying to Pittsburgh, where he and running mate Joe Biden will kick off a bus tour of Pennsylvania, Ohio and Michigan. Their goal is to maintain the buzz of a convention that culminated Thursday night with Obama addressing an energetic, flag-waving crowd of 84,000 packed into Denver's pro football stadium.
"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," Obama told the adoring crowd at Invesco Field. "America, this is one of those moments."
In the jam-packed football stadium, Obama promised an end to eight years of "broken politics in Washington and the failed policies of George W. Bush" and argued that McCain "doesn't get it."
He pledged to cut taxes for nearly all working-class families, end the war in Iraq and break America's dependence on Mideast oil within a decade. Portraying a McCain administration as a continuation of the current Bush White House, Obama said, "On Nov. 4, we must stand up and say: 'Eight is enough."'
Polls show a tight race between Obama and McCain, with some two months before the election and three high-stakes debates.
Obama accepted his party's nomination on the 45th anniversary of Martin Luther King Jr.'s "I Have a Dream" speech. He alluded to the historic parallel -- and its promise -- toward the end of his 44-minute speech.
"What the people heard ... people of every creed and color, from every walk of life -- is that in America, our destiny is inextricably linked. That together, our dreams can be one," Obama said.
Scattered around the stadium, some wept when Obama entered.
"I'm crying because I was around when Martin Luther King died and when John F. Kennedy died, and it's a long time since then and a long time to get back the dream," said Francino Norman of Miami. "This is history. I will tell my grandchildren about this."
Obama criticized McCain's support for the war in Iraq, while invoking Franklin Roosevelt and John F. Kennedy as proof that Democrats could be strong on defense.
"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. "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."
In response, McCain's campaign said, "Tonight, Americans witnessed a misleading speech that was so fundamentally at odds with the meager record of Barack Obama."
The Obama campaign emphasized the next phase of the campaign by encouraging supporters in the stadium to use their cell phones to send text messages to friends and to call thousands of unregistered voters from lists developed by the campaign.
Obama's campaign has identified 55 million voting age Americans across the country who are not registered to vote.
Obama entered the Democratic convention still needing to win over many of Clinton's supporters. Some Clinton delegates arrived in Denver wary of Obama, still sore over their epic nominating battle.
Obama's speech followed two days of full-throated endorsements by his one-time rival and her husband, the former president. Hillary Rodham Clinton issued a short statement Thursday night praising Obama's speech.
Sari Bourne stood in the crowd Thursday night and cried while holding an American flag against her cheek.
"I worked on the Hillary Clinton campaign for a year and I've come to the realization that he's the one to change this country," said the 23-year-old New Yorker.
On the other side of the globe, Obama's relatives in Kenya watched his speech at the home of Obama's uncle, Said Obama, in Kisumu, more than 300 miles from the capital, Nairobi.
Said Obama told The Associated Press in a telephone interview that he believes his nephew's success signals a change in race relations in America.
"Race is a problem in America," he said. "But let's hope that Americans are going to address the problems that are bedeviling the country."