WASHINGTON – The gloves are officially off between U.S. President Barack Obama and Mitt Romney now that the Republican front-runner’s only real competition has exited the party’s gruelling presidential race.

Less than 24 hours after Rick Santorum’s departure from the contest — described by Romney as a “good day for me” — the former Massachusetts governor was on the hot seat in a bruising battle with a well-funded, well-oiled Obama re-election machine that provided a glimpse of the seven months ahead.

In a conference call with reporters, a trio of Romney’s top campaign advisers faced tough questions about his insistence a day earlier that 92 per cent of jobs lost in the U.S. since Obama took office were held by women, a much-disputed reading of federal statistics.

Romney’s been trying to gain ground with women in the face of numerous polls suggesting they prefer Obama by as much as 20 percentage points. Women represent almost 53 per cent of the American electorate.

His campaign officials were asked three times on Wednesday to point to Obama policies that have hurt women. They offered nothing specific in response.

They were also asked if Romney supported the so-called Lilly Ledbetter Act, which essentially promotes equal pay for equal work and was the first bill Obama signed into law as president. A campaign official replied that he’d have to get back to the reporter on the question.

Within a couple of hours of the call wrapping up, Romney’s campaign sent out an email in response: “Women account for more than 92 per cent of jobs lost under Barack Obama. Of course Mitt Romney supports pay equity for women. The real question is whether President Obama supports jobs for women.”

Another Romney official said the candidate had no intention of changing the Lilly Ledbetter law.

But with lightning speed, Obama’s campaign team had already pounced on the misstep, distributing a statement from Lilly Ledbetter herself.

“I was shocked and disappointed to hear that Mitt Romney is not willing to stand up for women and their families,” Ledbetter, a former Goodyear employee who was paid significantly less than her male colleagues for two decades at an Alabama tire-making factory.

The 73-year-old Ledbetter became a women’s activist after the Supreme Court ruled that she was not entitled to any compensation from Goodyear because she filed her claim more than 180 days after receiving her first discriminatory pay cheque.

The Lilly Ledbetter Act lifted the statute of limitations for women who sue to receive equal pay for performing the same jobs as men.

“Anyone who wants to be president of the United States shouldn’t have to think about whether they support pursuing every possible avenue to ensuring women get the same pay for the same work as men,” Ledbetter said in her statement. “Our economic security depends on it.”

In addition to that smackdown, there was more bad news for Romney in a new ABC News/Washington Post poll that shows he’s trailing Obama by 19 percentage points in terms of general popularity.

Fifty per cent of those surveyed viewed Romney unfavourably, while 34 per cent have a favourable opinion. That’s the lowest level for any leading presidential candidate during a primary season in the 28 years that ABC News and the Post have been conducting such polls.

Romney has been taking aim at Obama for months, preferring to annihilate his rivals for the nomination by out-spending them on the campaign trail while reserving most of his oratorical scorn for the president.

Obama, meantime, has rarely mentioned Romney’s name, making only veiled references to him this week while pushing for tax reform, a centrepiece of his re-election campaign as he struggles with a still-sputtering economy and health-care legislation that’s in judicial jeopardy.

But his campaign team has begun to excoriate Romney in recent days, even putting out a statement soon after Santorum’s departure saying the multi-millionaire would not be able to buy the presidency the way he’s bought the nomination.

Romney was sanguine on Wednesday.

“We are getting started with a general election campaign, and people will get to know me better and they will get to know (Obama) better as well,” Romney told Fox News.

“And they will look at his record, which ultimately is the record upon which a campaign is going to be waged.”

Obama, meantime, kept up his demands that Congress pass the so-called Buffett rule, a tax measure that would ensure America’s millionaires pay tax at the same rate as the middle class.

The proposal is named after billionaire investor Warren Buffett, an Obama supporter who has called for tax hikes on the wealthy after observing last year that his secretary pays tax at a higher rate than he does.

“It’s just plain wrong that middle-class Americans pay a higher share of their income in taxes than some millionaires and billionaires,” Obama said at the White House, surrounded by an assortment of millionaires and their assistants who support the Buffett rule.

It’s all part of Obama’s efforts to portray the Republican party — and its wealthy presumptive nominee — as being more concerned about rich Americans holding onto their wealth than it is about average working men and women.

Republican proposals to cut taxes for the wealthy, Obama said, would result in spending cuts to programs that fuel economic growth and benefit the middle class, senior citizens and the poor.

“They want to double down on some of the inequities that already exist in the tax code,” he said. “We can’t afford to keep spending more money on tax cuts for wealthy Americans who don’t need them and weren’t even asking for them.”

He reiterated his campaign’s reminder that Ronald Reagan himself, the former president and beloved conservative icon, also once pushed for tax equality.

“I’m not the first president to call for this idea that everybody has got to do their fair share,” he said, adding another commander-in-chief had once called it “crazy” that bus drivers paid taxes at higher rates than multi-millionaires.

“That wild-eyed, socialist, tax-hiking class warrior was Ronald Reagan,” he said to laughter.