Minnesota congresswoman Michele Bachmann has ended her campaign for the White House.
The Tea Party favourite made the announcement in Des Moines, Iowa, where she finished a disappointing sixth in the state's caucuses on Tuesday.
Her withdrawal from the field leaves six other contenders in the presidential race.
They are vying to become the Republican nominee to challenge President Barack Obama for the White House in November.
Former Massachusetts Governor Mitt Romney won Iowa's caucuses by a wafer-thin margin over former Pennsylvania Senator Rick Santorum.
There was speculation that Texas Governor Rick Perry, who finished fifth, might also drop out, but he tweeted on Wednesday: "Here we come South Carolina!!!"
The Perry campaign confirmed he would attend a Republican debate on Saturday in New Hampshire.
Mrs Bachmann, 55, told a news conference on Wednesday: "Last night the people of Iowa spoke with a very clear voice and so I have decided to stand aside."
She said she had "no regrets".
Mrs Bachmann did not endorse another candidate, but said: "I believe that we must rally around the person that our country and our party and our people select to be that standard bearer."
She spoke at length about her reasons for entering the race, denouncing President Obama's healthcare reforms as "left-wing social engineering", which "endangered the very future" of the US.
Mrs Bachmann, who pitched for the evangelical Christian vote, was briefly the front-runner back in August. But after fundraising woes and staff departures, she could only win 5% of votes in the state where she was born.
After a nailbiting count Mr Romney was declared the winner in Iowa in the early hours of Wednesday.
He squeaked to victory by just eight votes, with 30,015 ballots (24.55%) against 30,007 for Mr Santorum (24.54%).
Texas congressman Ron Paul, a libertarian-leaning anti-war candidate who has attracted many younger voters, came third with 21.5% of votes.
A record 122,000 straw ballots were cast by Republicans in the largely rural state.
Before his wafer-thin victory, Mr Romney announced another high-profile endorsement, this time from Arizona Senator John McCain, the 2008 Republican nominee.
The focus now turns to New Hampshire, Mr Romney's political heartland, where a primary election will be held on Tuesday.
Mr Romney's well-financed political machine has snapped up television advertising space in the key swing state of Florida, which holds its primary at the end of this month.
He is already spending hundreds of thousands of dollars on TV ads in New Hampshire and South Carolina.
Meanwhile, former House Speaker Newt Gingrich, who came fourth in Iowa, set his sights on Mr Romney.