For his Democrat supporters, the 46-year-old African-American Senator from Illinois has found the key to moving on and motivating voters to participate in selecting the next US president. Obama's message is one of hope over fear and he has coined a phrase to symbolise it: political addition not division. Voters in the Iowa college, who met to cast the first real votes of the 2008 presidential election campaign, have lapped it up.

In doing so, they have clipped the wings of high-flying Hillary Clinton and raised the prospect of America's first black president. The fact Senator Obama's initial victory came from a state in which 95per cent of its residents are white makes it even more remarkable. But it's still a long way to the White House.

The Iowa caucus result has smashed two widely held assumptions. For Republicans, it has shown that personality is more important than paid advertising. The White House is not for sale. Small-spending Mike Huckabee demolished his big-spending opponents by staying positive and mobilising the religious vote. But not too much should be read into the Iowa verdict because the Republican race has yet to begin in earnest.

For Democrats, the Iowa result is much more significant. It may well come to be seen, Senator Obama has claimed, as the moment when it all began. Senator Obama's Iowa win represents the first real crack in the Bush-Clinton-Bush dynastic power exchange that has dominated US politics for the past two decades. Hillary Clinton's third position in the Iowa caucus race will not puncture her hopes of becoming president, but it is a serious setback.

Given the soaring rhetoric of Senator Obama's victory speech and the way in which he will, for a week at least, dominate the US news agenda as a credible candidate, Senator Clinton must reassert her position as frontrunner quickly or her opportunity will be lost. As The Weekend Australian's Washington correspondent Geoff Elliott writes today, the Iowa result is hugely significant for Senator Obama. It may finally unlock for him the black vote that has tended to stick to Senator Clinton because many did not believe he had a chance of becoming president. His solid victory in a state with less than 5 per cent African-Americans has proved them wrong.

If Iowa has put momentum behind Senator Obama's push, it has also shown that momentum is running the Democrats' way at this point. More than 220,000 Democrat supporters turned out to vote in the complicated and time-consuming college process, more than double the number in 2004. The Democrat turnout was nearly twice as large as the Republican vote, which was also up from four years ago.

The Iowa contest was not as significant for the Republicans as the Democrats, however, because the national frontrunner, former New York mayor Rudy Giuliani, chose to bypass the Iowa college, and Tuesday's New Hampshire contest, to concentrate on Florida on January 29 and the Super Tuesday vote on February 5.

The win to Mr Huckabee in Iowa, on the back of an influx of born-again Christian voters, is unlikely to prove decisive in the overall Republican campaign. More significant may be the respectable showing of John McCain, who was battling it out for third spot with former actor Fred Thompson behind the big-spending Mr Romney.

At this early stage, it is impossible to predict where the 2008 presidential race will go. Too much should not be made of the Iowa result. Despite claims it has a history of picking the future presidential candidates, it also has a history of getting it wrong -- remember Bob Dole and Richard Gephardt.

Making things harder to predict is the fact that in 2008, the contest is considered to be the least predictable in 80 years. The major issues are also ill-defined and the campaign could be swamped at any time by external shocks, such as a new security threat or bad economic news. For the Democrats, uncertainty would favour Senator Clinton, who is making her pitch for nomination on the basis of experience, pitted against what she says is Senator Obama's youth, hope and enthusiasm.

For the Republicans, a combination of better news from Iraq, where the troop surge has quelled sectarian violence in Baghdad, together with the uncertainty caused by the assassination of Benazir Bhutto in Pakistan, has helped to fuel Senator McCain's extraordinary political comeback. Unlike other candidates, Senator McCain has been a consistent supporter of the war in Iraq. But at 71 years of age, he would be the oldest first-term president in UShistory.

As such, Senator McCain's candidacy is in sharp contrast to Senator Obama's message of social and political renewal which has proved to be attractive in Iowa. The Wall Street Journal's Peggy Noonan says that more than anyone else, Senator Obama turns the page of history.

He represents a break with the past, a break with the tired old argument, a break with the idea of dynasty, the idea of the machine, the idea that there are forces in motion that cannot be resisted. Confirming his victory in Iowa, Senator Obama said voters had chosen hope over fear and sent the message that change is coming to America.

He has pledged to fix healthcare, protect local jobs, deliver middle-class tax breaks and free the nation from the tyranny of oil dependency. His rhetoric is to bring the troops home, but he will not abandon the Middle East. Senator Obama has a long way to go but, after Iowa, he is the one to watch as America begins to send the message that it, like Australia, is ready for a new generation.