Democratic Illinois Senator Barack Obama and former Arkansas governor Mike Huckabee, a Republican, have been declared the winners of their presidential caucuses in Iowa, the first test in the race for the White House.

Presidential hopeful Senator Barack Obama, with his wife, Michelle, and daughter Sasha, acknowledges supporters Thursday after winning the Iowa Democratic caucus. Analysts said Obama's victory has damaged Hillary Clinton's front-runner image.
(M. Spencer Green/Associated Press)

Obama, who had been in a tough three-way battle against Senator Hillary Rodham Clinton and former senator John Edwards, won convincingly. Vying to become the first black president, Obama had 37 per cent support among Democrats. Edwards appeared headed for second place with Clinton finishing a close third.

"They said this day would never come. They said our sights were set too high," a raspy-voiced Obama told his crowd of supporters Thursday night.

"They said this country was too dividing, too disillusioned to ever come together around a common purpose. But on this January night, on this defining moment in history, you have done what the cynics said we couldn't do."

The poor showing of Democratic Senators Joe Biden and Chris Dodd prompted them to abandon their presidential bids.

Huckabee, who came from behind in recent weeks with support from evangelical Christians, had been in a tight race with former Massachusetts governor Mitt Romney. He was winning with 34 per cent support, compared with 25 per cent for Romney. Former senator Fred Thompson and Senator John McCain battled for third place.

"A new day is needed in American politics, just like a new day is needed in American government," Huckabee told his supporters. "It starts here but it doesn't end here. It goes all the way through the other states and ends at 1600 Pennsylvania Avenue."

Former Arkansas governor Mike Huckabee won Iowa's Republican caucuses despite being seriously outspent by competitor and former Massachusetts governor Mitt Romney.
(Mandi Wright /Detroit Free Press/Associated Press)

Rudy Giuliani, the former New York City mayor considered at one time the national front-runner but who has seen his support slip, trailed in sixth place, having effectively bypassed Iowa to concentrate his resources on big states like Florida.

Leading up to the Iowa caucus, Clinton's campaign focused on her experience and time in the White House during her husband's two-term presidency. But with Obama climbing in the polls, Clinton's campaign began to rap the junior Illinois senator over his inexperience.

Obama, who campaigned on a theme of change and bipartisan co-operation, rebuffed Clinton's charges and questioned whether being the spouse of a president makes one qualified for the role.

'Not a good sign' for Clinton: analyst

Despite her defeat, Clinton vowed to continue the fight.

"We have always planned to run a national campaign," the former first lady told supporters at a noisy rally attended by her husband and their daughter, Chelsea. "I am so ready for the rest of this campaign, and I am so ready to lead."

For Clinton, who wants to become the first female commander-in-chief, analysts said the loss in Iowa challenges her front-runner status and changes the dynamics of the Democratic race.

"This is not a good sign for [the] Clinton campaign," analyst Donna Brazille said.

Edwards, the party's vice-presidential nominee in 2004, had portrayed himself as the defender of the little guy. He cultivated the union vote and the rural vote and campaigned relentlessly in Iowa hoping to build up enough steam to give him staying power in the primaries to follow.

Despite Huckabee's victory, it is not known whether he can translate that to wins in other states, where he faces opponents with deeper pockets.

Huckabee's conservative views about abortion and gay marriage had rallied the religious right and helped him shoot up in the polls. Some see Romney as a flip-flopper because he changed his political stance on abortion, having once supported abortion rights.

'I intend to keep making up ground': Romney

Romney, a successful businessman, had narrowed the gap with negative ads about Huckabee's record of being more forgiving toward illegal immigrants, granting clemency to criminals and raising taxes. He also outspent Huckabee by a ratio of 20 to 1.

But Romney noted that he had trailed Huckabee by more than 20 points a few weeks ago.

"I've been pleased that I've been able to make up ground and I intend to keep making up ground, not just here but across the country," he said.

Romney's Mormon faith had also become an issue during the campaign, causing concern among some Christian conservatives who view it as a cult. Huckabee himself raised questions about some of the religion's beliefs in an interview, but later apologized.

The issue prompted Romney to deliver a speech in December, asking Americans not to reject his presidential bid because of his Mormon faith.

The caucus vote is considered the official kickoff to the November 2008 presidential election. Voters from both parties choose delegates to attend party conventions later this year.

The winners in Iowa will likely give the candidate a boost in New Hampshire, where independents can vote in either primary. But it should be clear by Super Tuesday on Feb. 5, when more than 20 states weigh in, who the nominees will be.

With files from the Associated Press