Today's announcement by Senator Barack Obama that he will seek the Democratic nomination for the US presidency should be an inspiring occasion, and a highly symbolic one, too. The 45 year-old senator for Illinois has chosen to stake his claim at the same State Capitol building in Springfield where Abraham Lincoln, the liberator of America's slaves, served his political apprenticeship. Mr Obama's many fans - and perhaps some of his rivals too - believe he could be elected the first black President of the United States.

Much can happen between now and November 2008. The public announcement is the very first step on a testing marathon of a campaign. Even to have a realistic shot at the presidency, Mr Obama has to raise a mountain of money and continue to raise it. He has to recruit a veritable army of advisers. He has to tailor his appeal separately to the states where the early primaries are held, and then broaden it again for the states whose delegates will decide the party convention. Only then will his name even figure on the presidential ballot. He then has to possess the reserves of energy necessary to criss-cross the country many times until the final exhausting and exhilarating coast-to-coast sprint to get the vote out.

At this very early stage, this comparatively young senator has a lot going for him. He clearly has the appetite for higher office and appears to have the energy for the rigours of the campaign. He has personal charisma and eloquence in abundance. And while he has only two years behind him in the US Senate, he is no political novice. He has eight years' experience in his state legislature. It is executive - rather than political - experience that he lacks.

He also has one signal policy advantage. In an election where the Iraq war is likely to be an issue, Mr Obama has the distinction of having opposed it all along. This was an easier course, to be sure, for a state politician who did not have the national security card waved in his face by the Bush White House at every turn. But it gives his arguments a consistency, and allows him to claim a degree of foresight, that his more experienced rivals will be unable to match.

These are, it cannot be stressed too much, very early days in the 2008 presidential race. But the enthusiastic head of steam Mr Obama's incipient campaign has already built up starts the contest on an especially positive note. It marks a new stage in the long overdue entry of black Americans into the political mainstream. In Colin Powell, the US had its first black chairman of the Joint Chiefs of Staff and its first black Secretary of State. In Condoleezza Rice, it has had its first black woman in the top echelons of the administration. There are more black members of this Congress than of any previous one. The time must surely come when colour is no longer remarked upon in US politics. The US, it should be noted, is streets ahead of Britain in this respect.

Mr Obama's presence will not be the only novel feature of the 2008 campaign. The most open for very many years, it will be a campaign of firsts. Hillary Clinton, senator for New York and wife of Bill, will be the first woman with a realistic chance of the nomination. Mitt Romney, the governor of Massachusetts, will be the first Mormon candidate with national appeal. Add into the mix the colourful former mayor of New York, Rudy Giuliani, senator John McCain of Arizona, whose hero's biography and Straight Talk Express brought him a national following in 2000; and John Edwards, the populist lawyer and former senator from North Carolina - and there is already a contest to savour. Bring it on, we say. The era of George W Bush cannot end too soon.