"I would welcome a circumstance where there was such a consensus in this country that we said, 'We don't want to have abortion in this country at all, period.' That would be wonderful," Romney said.
"But," he added, "that's not where we are. ... Where America is is ready to overturn Roe v. Wade and return to the states that authority" to decide if abortion should be legal.
The Obama ad uses a clip from Romney’s remark to accuse him of hiding his real position on abortion from voters.
"Trying to mislead us? That's wrong," the ad's female narrator says in voice-over. "But ban all abortions? Only if you vote for [Romney]."
A spokeswoman for the GOP nominee said the Obama campaign is trying to distract women from the economic mess the president has failed to fix.
"President Obama's campaign continues to mislead voters in a desperate attempt to distract from this president’s failed economic record," said Amanda Henneberg. "Five and a half million women are struggling to find work in the Obama economy, and they are suffering from record unemployment under this president."
The gender gap favoring Democrats has narrowed in recent weeks, with Romney pulling even with Obama among women in some swing states. Pollsters attributed the shift to Obama's weak performance in the first presidential debate.
Abortion came up five days after that event when Romney said that legislation to restrict abortion rights was not "part of my agenda."
The comment seemed to conflict with his past statements in support of 20-week abortion bans and "personhood" bills, which would give fetuses legal rights.
The Obama campaign soon charged Romney with playing politics in order to appeal to women — accusations that continued Thursday.
"Mitt Romney is dishonestly trying to claim that he isn’t staunchly opposed to a woman’s right to choose," the Obama campaign said in a statement.
"On the campaign trail and in a recent television ad, Romney is cynically hiding his real position from the American people because he knows it’ll hurt his chances to win. ... [He] may try to change his image just weeks before Election Day, but he can’t change the fact that women can’t trust him."
Romney's campaign has said that he "will be a pro-life president," and on the campaign trail, Romney has promised to defund Planned Parenthood and bar U.S. foreign aid from paying for abortions if he is elected.
"No false, cheap political attacks from President Obama and his campaign can change the fact that women cannot afford another four years like the last four years," Henneberg said in response to the Obama ad.
"Mitt Romney will lead us to a real recovery so that women — and all Americans — can succeed, and he will ensure that the next four years are better than the last four."