There was just one word on the home page of the Barack Obama website yesterday: Change. With only hours to go, the Democrats were advertising Change We Need rallies and Change the World T-shirts. The presidential candidate's slogan is: “Change we can believe in” - “I'm asking you to believe not just in my ability to bring about real change in Washington, I'm asking you to believe in yours,” says the man who would be commander in chief.

If the polls are right and Mr Obama is indeed declared the first black president of the United States early tomorrow morning nobody can be in any doubt that America has decided it is time for a change. “Change to what?” many will ask with some justification. But in this crossroads election - that is a choice between different cultural as well as political futures - the voters have opted for the new over the old.

Right to the end, John McCain was pitting his experience against his rival's lack of it. The Republicans have been playing voters in swing states a recording of Hillary Clinton saying that “in the White House there is no time for on-the-job training”. Just as it looked initially as if the former First Lady would snatch the Democratic nomination from the new kid on the block, so some assumed that the 72-year-old Vietnam vet would seize the crown from the young pretender. The electorate, however, appears to have decided that it is time for a novice.

And this is, of course, a message that has resonance in Britain. The presidential contest is a political prototype, the Urtext of election campaigns, because in the end all contests boil down to a choice between experience and change. It can be framed in different ways - the future against the past, fear rather than hope, “better the devil you know” versus “it can't get any worse”. In television terms, it's The West Wing or Yes, Minister; during the primaries, the Obama team described it as “magic versus the machine”.

And once the voters have decided it is time for a change then it is very hard to counter that mood by playing the experience card. In 1979 Margaret Thatcher swept to power by declaring: “Labour isn't working”; in 1997 Tony Blair won with the slogan: “Things can only get better.” The closest we have got to an exception in this country in recent history is 1992 - when the Conservatives clung on against the odds, but even then they had a relatively new leader, John Major, who had dumped his predecessor's most unpopular policy - the poll tax. He was also up against Neil Kinnock, who was not trusted on the economy.

According to Andrew Cooper, the director of the polling company Populus, British voters are as anxious for change as American ones. About 85 per cent of people on both sides of the Atlantic think that their country is “going in the wrong direction”. In one recent poll in this country, 75 per cent said Britain's best years were behind it. The downturn is likely to exacerbate the gloomy mood.

Gordon Brown clings to “experience” like Charlie Brown's friend Linus hugs his comfort blanket. As the economy enters choppy waters, he sees himself as the weather-beaten sea captain who can steer the good ship Britannia to safety, leaving his dilettante rival standing, glass of champagne in hand, on a passing yacht. He is Not Flash, Just Gordon, who prefers competence to charisma, a “safe pair of hands” who is more comfortable with intellectual endeavour than emotional intelligence. Like Hillary Clinton, he is an admirer of Mark Penn, the political consultant who argues that likeability - what he calls “buddy potential” is overrated in politics. His conference soundbite “it's no time for a novice” was not just a slapdown to the two Davids, Cameron and Miliband, it is also his personal slogan between now and the next election. But experience will not be enough - as one Cabinet minister puts it: “Gordon has done well in the past few weeks, he's won permission to be auditioned again but at the election he's still going to be auditioned about the future.”

Mr Cameron by contrast is trying to present himself as the candidate of “change”. Having brought social liberalism and Converse trainers to the Tory party he now wants voters to believe that he is best placed to modernise the country too. He is consciously trying to emulate Mr Obama's campaign by presenting himself as the youthful idealist who wants to create a “new kind of politics”. The Conservative conference slogan - “Plan for Change” - was filched directly from the Democrats; the Tories are trying to replicate the way in which the centre-left party in the US has used the internet to communicate with supporters and raise money. Although the Conservative Party should have a natural affinity with the Republicans - and John McCain even spoke at their conference two years ago - Boris Johnson is not the only senior Tory who wants the Democrats to take the White House. As one senior strategist puts it: “The change argument will be massively strengthened if Obama wins, the novice argument will be shattered.” But Mr Cameron needs to do more to show that he and George Osborne can be trusted to run the economy

Lord Malloch-Brown, the Foreign and Commonwealth Office Minister, who was a political consultant before he joined Mr Brown's Government of all the talents, draws a diagram rather like the points of a compass to portray election campaigns. At either end of the vertical line he puts the words Change and Experience, at the ends of the horizontal line he writes Strength and Weakness. It is true that if the mood of the country is right change will trump experience - unless the appeal of the new is outweighed by a candidate's weakness on an issue that really matters. As America goes to the polls, Mr Brown should worry about the momentum for change, but Mr Cameron should also be concerned about the “unless” factor.

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