Already scrambling to steady a struggling campaign, Republican Mitt Romney confronted a new headache Monday after a video surfaced showing him telling wealthy donors that almost half of all Americans "believe they are victims" entitled to extensive government support.

He added that as a candidate for the White House, "my job is not to worry about those people."

President Barack Obama's campaign quickly seized on the video, obtained by the magazine Mother Jones and made public on a day that Romney's campaign conceded it needed a change in campaign strategy to gain momentum in the presidential race.

"There are 47 per cent of the people who will vote for the president no matter what," Romney is shown saying in a video posted online by the magazine. "There are 47 per cent who are with him, who are dependent upon government, who believe that they are victims, who believe that government has a responsibility to care for them, who believe that they are entitled to health care, to food, to housing, to you name it."

"Forty-seven percent of Americans pay no income tax," Romney said.

Romney said his role "is not to worry about those people. I'll never convince them they should take personal responsibility and care for their lives."

Romney's campaign did not dispute the authenticity of the video, instead releasing a statement seeking to clarify his remarks. "Mitt Romney wants to help all Americans struggling in the Obama economy," spokeswoman Gail Gitcho said. "He is concerned about the growing number of people who are dependent on the federal government."

About 46 per cent of Americans owed no federal income tax in 2011, although many of them paid other forms of taxes. More than 16 million elderly Americans avoid federal income taxes solely because of tax breaks that apply only to seniors, according to the nonpartisan Tax Policy Center.

Obama's campaign called the video "shocking"

"It's hard to serve as president for all Americans when you've disdainfully written off half the nation," Obama campaign manager Jim Messina said in a statement.

An Obama adviser said the Democratic campaign might use Romney's comments from the fundraising video in television advertisements. The official wasn't authorized to discuss campaign strategy publicly and requested anonymity.

The private remarks are the latest in a string of comments from the multimillionaire Republican businessman whom Democrats have criticized as out of touch. During the primary campaign, Romney insisted that he was "not concerned" about the very poor, said he knew what it felt like to worry about being "pink-slipped," and said that his wife drove a "couple of Cadillacs."

Aides to Obama's campaign said the latest video would help them continue to make the case that Romney doesn't understand the concerns of average Americans.

Voters say they believe Obama has a better understanding of their problems and concerns than Romney does. A CBS/New York Times poll showed 60 percent of likely voters said Obama understands the needs and problems of people like them, while 37 percent said he did not. For Romney, the same question found that 46 per cent felt he did understand people's needs, 48 per cent said he didn't.

The remarks came at a closed-door fundraiser that Mother Jones reported occurred after Romney had clinched the GOP nomination. To protect the identity of the person who provided the remarks, Mother Jones blurred out the video and did not provide the date or location of the fundraiser.

Romney formally clinched the nomination May 29 and formally accepted it last month at the Republican convention in Tampa.

Many of the Americans who owe no income tax are reprieved because basic exemptions — such as the "standard deduction" — took their taxable income below the cutoff levels. The other half rely mainly on a variety of tax breaks, such as the credit that helps offset child care costs.

These Americans range from the very poor to solidly middle-class families with jobs, homes, cars and vacations. The Tax Policy Center says "relatively few nontaxable households" have incomes exceeding $100,000; families that make between $50,000 and $100,000 often owe no income tax because of breaks for their kids and for education.

Americans who pay no federal income tax still often pay an array of other taxes. They include payroll taxes for Social Security and Medicare, sales taxes, property taxes and state and local taxes.

A handful of extremely wealthy families do not pay federal income taxes. This summer the Internal Revenue Service reported that six of the 400 highest-earning households in America owed no federal income tax in 2009.

Still, many are low-income Americans. According to the August 2010 AP-GfK poll, a majority of Americans who make less than $30,000 a year are Democrats. But 27 per cent identify as Republicans, and 15 percent say they're independents. About 57 percent say they will vote for Obama, while 38 percent back Romney. About 43 percent identify themselves as conservatives.

Obama faced a similar moment in the 2008 campaign, when he told donors that many Americans who are angry about their struggles "cling to their guns or religion."

Romney's running mate, Wisconsin Rep. Paul Ryan, made reference to that remark Monday at a campaign event in Des Moines, Iowa.

"I remember that one time when he was talking to a bunch of donors in San Francisco and he said people like us, people from the Midwest like to cling to their guns and religion," Ryan said.

Ryan went on: "And I've got to tell you this Catholic deer hunter is guilty as charged and proud to say so. That's just weird. Who says things like that? That's just strange."