Article published on the 2008-08-29 Latest update 2008-08-29 15:35 TU
After a rapturous reception from the massive crowd and an audience of millions for live TV broadcasts across the US, Obama prepared his supporters for a tough campaign.
"It's going to be hard," he told a reception for fundraisers after his speech.
With rival Republicans holding their convention in Minnesota next week, Obama predicted "they'll have a whole lot of fun with us", predicting that they will "change some minds, and persuade, and then the race is on".
Republican candidate John McCain's campaign declared Obama's speech "misleading", insisting that he is "still not ready to be president".
Democratic presidential candidate Barack Obama (D-IL) (R) leaves the stage with his wife Michelle (2nd L) and and children Malia (L) and Sasha (2nd R)
(Photo: Reuters)
His erstwhile rival for the Democratic nomination described the address as bold and optimistic.
"His speech crystallised the clear choice between he and Senator McCain. Four more years of the same failed policies or a leader who can tackle the great challenges we face: revitalising our economy and restoring our standing in the world," she said.
"You are looking at the first real challenge to the conservative juggernaut that established itself in this country with the election of Ronald Reagan in 1980," academic Elizabeth Sanders told RFI.
While saying that Obama is "not a radical", she says that he "constitutes much more of a repudiation" of right-wing principles than recent Democratic candidates.
Obama's speech stressed his differences with McCain, portraying the Republican candidate as out of touch with ordinary Americans.
"It's not because John McCain doesn't care. It's because John McCain doesn't get it," Obama said, attempting to connect with the blue-collar voters he must attract to win.
He also tried to answer opponents' questioning of his patriotism and stressed McCain's links to the current Bush adminstration, which he portrayed as a breach with American traditions.
"America, we are better than these last eight years," Obama said. "We are here because we love this country too much, to let the next four years look like the last eight. On November 4, we must stand up and say: 'Eight is enough'."