As the first votes were cast in the White House election, Obama placed the 47% remarks at the heart of his campaign, telling supporters in Virginia that change in cannot be achieved in one term and "it can't happen if you write off half the nation before you take office".
Romney's comments were caught on a secretly recorded video when the Republican presidential candidate addressed a small group of wealthy donors in May.
The attack was reinforced in new ads released Thursday. In one, Romney's voice is heard dismissing the 47% of the population who he said are dependent on the government and take no responsibility for their own lives. On screen, as Romney speaks, are pictures of the groups the Democrats suggest he was referring to: the elderly, veterans, Latinos, children and working-class women.
It is a potent election message, and Romney's remarks are proving to be one of the most destructive moments of the whole White House campaign.
Another Obama ad deals with "economic patriotism", a new label for the president's economic promises, which include creating 1m manufacturing jobs and hiring thousands of new teachers.
They are to be broadcast in seven swing states: Virginia, Florida, Ohio, New Hampshire, Iowa, Colorado and Nevada. But they are not being shown in North Carolina, a sign that the Obama campaign may have written the state off as a gain for Romney.
The "economic patriotism" promotes economic growth from the bottom up and contrasts this with Romney's trickle-down approach.
"This country doesn't succeed when only the rich get richer," Obama said in his speech. "We succeed when the middle class gets bigger, when there are ladders of opportunity for all who strive to get into the middle class, when everybody who's willing to work hard has a chance to get ahead and live up to their God-given potential."
Then, turning directly to the secret video, Obama added: "I don't think we can get very far with leaders who write off half the nation as a bunch of victims who never take responsibility for their own lives."
Both Obama and Romney were campaigning in Virginia on Thursday in areas with a strong military presence. The president was in Virginia Beach while Romney was in Springfield.
Obama opted for a broad appeal to voters while Romney flailed about in the wake of disastrous poll figures showing him badly trailing the president in swing states. Obama is ahead in Virginia in spite of predictions he would not be able to hold it after his 2008 win.
Early voting began in Iowa on Thursday and starts in Ohio next week and elsewhere round the country. An estimated 30%-40% of those voting will have cast their ballots before election day November 6.
In his speech, Obama, echoing Romney's secret video, said that wherever he visited in America, including Virginia, he did not find victims as Romney contended but hardworking Americans.
"I see students trying to work their way through college. I see single moms, like my mom, putting in overtime to raise their kids right. I see senior citizens who have been saving for retirement your entire lives," Obama said. "I see a whole bunch of veterans who served this country with bravery and distinction."
In what could be a rehearsal for the first presidential debate in Denver on Wednesday, he noted that Romney had picked up on a comment he had made that change in Washington does not come from the inside and that change in Washington had to come the outside.
"And for some reason, this got governor Romney really excited. And he rewrote his speech, and he stood up at a rally and he proudly declared: 'I'll get the job done from the inside' – which got me thinking, what kind of inside job are you talking about?," Obama said, proving that not only does he have better delivery than Romney, he has better speech-writers.
As the laughter subsided, Obama continued: "Because if it's the inside job of rubber-stamping the top-down, lobbyist-driven agenda of this Republican Congress, we don't want that. If it's the inside job of letting oil companies write energy policy, insurance companies writing health care policy, outsourcers writing our tax code, we don't need that. If it's the inside job of trying to control the health care choices that women are perfectly capable of making themselves, we'll take a pass on that. We don't need an inside job."
He added, ramming home his point about Romney's speech: "In 2008, 47% of this country did not vote for me. But the night of the election, I said to all those Americans, I said, I may not have won your vote, but I hear your voice. I need your help. I will be your president, too."
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