Controversial US congresswoman Michele Bachmann has confirmed she is joining the race for the White House, with a fresh attack on Barack Obama.
It comes as a new opinion poll puts her neck-and-neck with establishment party front-runner Mitt Romney.
Ms Bachmann told supporters: "We cannot afford four more years of Barack Obama.
"Make no mistake about it Barack Obama will be a one-term president."
Ms Bachmann is often dubbed 'the new Sarah Palin' after the former vice-presidential candidate who also represents the views of the small government, low taxation Tea Party.
But the 55-year-old mother-of-five has outdone Ms Palin by joining the 2012 race.
She said: "We can’t be about big government as usual because then America will lose."
Iowa was a strategic choice for her launch. The state holds the first contest on the road to the Republican nomination.
She certainly has a chance and the poll that puts her level with Romney was no fluke.Political analyst Byron York
But her challenge will be to gain the trust of voters beyond hard-core conservatives.
In recent months she has struck a more serious tone after building a reputation for incendiary comments and gaffes.
She once referred to Mr Obama as being 'anti-American' and has been accused of playing fast and loose with facts on occasions.
On a political talk show at the weekend she was asked: "Are you a flake?" She said that was "insulting".
She certainly livens up a Republican race to face Mr Obama which has been underwhelming so far and which appears to be without a clear front-runner.
Political analyst Byron York told Sky News: "She certainly has a chance and the poll that puts her level with Romney was no fluke."
The race also includes former Speaker of the House Newt Gingrich, former governor Tim Pawlenty, former senator Rick Santorum and pizza executive Herman Cain.