The gender row threatened to complicate the Republican's push for a key segment of the electorate, and offered US President Barack Obama a boost as he sought to stem Romney's recent polling surge ahead of the November 6 election.
In one exchange of their fiery debate on Tuesday, Romney said he reviewed "whole binders full of women" when looking for those qualified to join his cabinet as governor of Massachusetts.
A heated debate unfolded online and on US media outlets Wednesday over whether the comment suggested an antiquated view of women in the workplace.
Obama was quick to respond on the campaign trail in Iowa and Ohio on Wednesday, the day after the debate.
"We don't have to order up some binders to find talented, qualified young women, to learn, to teach," Obama said before a 14,000-strong crowd, many of them female, under fall foliage at Ohio University in Athens.
Romney's oddball phrase took on a life of its own, trending on Twitter and inspiring a "Binders Full of Women" Facebook page which drew 330,000 "likes."
Someone rustled up a blog -- http://bindersfullofwomen.tumblr.com -- for fan art mocking the phrase.
One picture showed two white plastic binders with the words, "Binder full of women. If found please return to Mitt Romney."
Another featured a shot of Secretary of State Hillary Clinton saying "No one puts me in a binder, I work for the president."
Vice President Joe Biden also waded into the mockery.
"Whoa! The idea that he had to go and ask where a qualified woman was, he just should have come to my house. He didn't need a binder," Biden said.
Obama and Biden were keen to jump on Romney's embarrassment because it offered them an opening to court the women's vote following several recent polls suggesting their advantage in the so-called gender gap was fraying.
The president beat Republican John McCain among women by 13 points in 2008, and in what is shaping up as an even closer election this time, may need an even wider gender gap to be safe.
Romney himself wasted no time courting female voters on Wednesday, telling a rally in Virginia: "This president has failed America's women."
As he crisscrosses the nation, women ask him to bring down unemployment, improve schools and provide their children with better job prospects, Romney said.
"That's what the women of America are concerned about. And the answers are coming from us and not Barack Obama."
Obama's attacks built on Democratic assaults on Romney earlier this year when he highlighted conservative positions on abortion to court the more radical audience of the Republican Party primary.
The president's senior advisor David Plouffe said women's issues were going to become "increasingly important" in the dying days of the race, as both campaigns seek to drive up margins with core voters.
A USA/Today Gallup poll caused a stir this week because it found that Obama only led Romney by one percent among likely female voters in swing states, after having a wide lead earlier this year.
Obama's campaign disputed the poll methodology and said it was flagrantly inconsistent with surveys across the country.
Romney's political director Rich Beeson argued, however, that there was significant movement towards the Republican ticket among women.
Whatever the state of play, experts say votes of women in suburban areas in places like Colorado and Virginia have the potential to sway whole state races which could help decide who wins the White House.
Obama, who wore a pink breast cancer support bracelet Wednesday, did not confine his attacks on Romney to women in the workplace, but also accused him of wanting to curtail women's rights to contraception, a charge Romney denies.
Obama has also lacerated Romney over whether he would support the first bill he signed as president, the Lilly Ledbetter Act, which makes it easier for women to sue to get equal pay to men.
"I have got two daughters. I don't want them paid less than a man who is doing the same job," Obama said in Athens.
Romney in the debate refused to say whether he would have signed the act, though he did suggest he wouldn't change it.
As controversy raged Wednesday, Romney's former lieutenant governor Kerry Healey sent around a fundraising email offering him strong support.
"When Mitt Romney talks about women, when he says he believes that we can do any job a man can do, I know from experience that he's speaking from the heart," Healey said.
"In fact, of the 20 top positions in the Romney administration, 10 of them were filled by women, more than any other state in the nation."