Firebrand Republican Representative Michele Bachmann formally launched a bid for the White House on Monday, warning that the US “cannot afford” to re-elect President Barack Obama.

“America is at a crucial moment,” Ms Bachmann, a darling of the archconservative Tea Party movement and of Christian conservatives, declared in a speech to some 200 cheering supporters in the key heartland state of Iowa.

“We can’t afford four more years of failed leadership here at home and abroad,” the outspoken lawmaker from Minnesota said here in the town where she was born. “We cannot afford four more years of Barack Obama.”

Ms Bachmann, 55, pointed to the swelling US national debt, soaring gasoline prices, waves of home foreclosures, historically high unemployment, and took aim at Mr Obama’s signature health law, a magnet for conservative voter anger.

“We can’t afford the unconstitutional health care law that costs so much and delivers so little,” said Ms Bachmann, a prodigious political fundraiser who at times has raised eyebrows with superheated rhetoric and verbal missteps.

“We can’t afford four more years of millions of Americans who are out of work,” she said to voters in Iowa, home to a first-in-the-nation caucus that shapes the Republican presidential field. “And we can’t afford four more years of a foreign policy with a president who leads from behind and who doesn’t stand up for our friends like Israel, and who and who too often fails to stand against our enemies,” remarked Ms Bachmann. Mr Obama re-election campaign spokesman Ben LaBolt fired back that Ms Bachmann “talks about reclaiming the American Dream but her policies would erode the path to prosperity for middle class families”.

Mr LaBolt cited her support for a Republican budget plan “that would extend tax cuts for the richest Americans on the backs of seniors and the middle class” and push to repeal the most sweeping Wall Street overhaul law since the Great Depression of the 1930s.

Ms Bachmann garnered 22 per cent support among likely caucus participants compared to the former Massachusetts governor’s 23 per cent, according to the poll organised by the Des Moines Register newspaper.

Ms Bachmann, the only woman officially in the Presidential race thus far, won solid reviews for her performance in a recent Republican debate and has brought on Republican campaign veterans to steer her Presidential run.

But Republican insiders and independent analysts question whether her take-no-prisoners rhetorical style and fiercely conservative stances on social issues can win over the independent voters thought to decide US elections.

“She will have a hard time expanding her base,” according to John Pitney, a political scientist at Claremont McKenna College.

“I feel she is rational, she’s smart, and she’s competent to get us out of here. Some hard decisions have to be made,” gushed supporter Becky Bostwick, who attended the announcement rally with her five children.

One potential rival, Tea Party superstar and 2008 Republican vice Presidential nominee Sarah Palin, has kept people guessing on a possible Presidential run – leaving a void for Ms Bachmann to fill.

Ms Bachmann has a history of blunt, fiery, or inaccurate comments that have drawn unflattering media scrutiny, including the suggestion that some of her colleagues in the House of Representatives were “anti-America”.

She has also dismissed scientists’ warnings about climate change, and recently blundered by saying the opening shots of the American revolution were fired in New Hampshire instead of Massachusetts.

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