It's been conventional wisdom for months in Washington that the only way that the Democrats were going to lose this election was if Barack Obama just seemed too big a risk.

The desire for change has been so palpable for so long, the stench of failure around the Bush Administration so great, the mood of the country so grim, that only fear of the Democratic candidate's callowness and doubts about his alignment with the basic values of Americans could possibly stop him.

Now, as a campaign that seemed to have started 17 years ago winds down into its final 17 days, two important new realities have emerged.

First, the scale of the economic crisis has become so politically dominant that, even if Mr Obama were exposed in the next two weeks as a Manchurian Candidate, programmed by Islamic fundamentalists to subvert the very core of American life, there's a chance voters would still think: hell, at least he's not from Wall Street.

But the other thing that has happened is that Mr Obama has not only succeeded in uprooting much of the thicket of doubts about his own suitability and readiness. He has had the unusual good fortune to watch as his opponent has planted a whole forest of fearful uncertainties around his own fitness for the presidency.

In the course of an extraordinary few weeks, it has been John McCain, the 35-year veteran of public life, the genuine hero who almost gave his life for his country, who has looked like the dangerous risk that Americans cannot afford to take.

His erratic sorties into the financial mess have laid waste to the idea that he is safe in a crisis. His performance in three presidential debates made him look angry and disconnected, befuddled and hurt at the misfortunes that have befallen him.

Worst of all, his attempts - and those of Sarah Palin, his once promising running-mate - to destroy Mr Obama by association with the 1960s radical William Ayers have backfired. No one has seriously been taken in by the suggestion that Mr Obama harbours in his bosom a domestic terrorist who once tried to blow up the Capitol. The effort has bewildered voters who, when the economy is in danger of disappearing down a sinkhole of financial panic, have had to listen to one candidate for president ranting about someone they have never heard of.

It's a tragic way for Mr McCain's career to end. If there was any justice he would have been president eight years ago. Instead this mighty oak of American integrity and honour is in danger of being blown over by the combined hurricane forces of inescapable economic collapse and shoddy political exigency.

All this means that, instead of the close election that Americans thought they would have, there is a very good chance that they are heading for a blowout. Instead of acting as countervailing forces, the macro-political conditions (desire for change) have been reinforced by the micro-political forces (the appeal of the individual candidates).

This will have enormous political consequences. Mr Obama is on course to become the first Democrat to win more than 50.1 per cent of the vote in a presidential election since Lyndon Johnson in 1964.

Barring a last-minute miracle, he will be elected on the crest of a wave of Democratic triumph in Congress. The Democrats are likely to gain between six and ten seats in the Senate, giving them as many as 61 seats out of 100, and possibly another 20 in the House, giving them a majority of more than 70.

These data alone will place the 2008 election on a par with the transformative elections of the past 100 years. The only two occasions in the last century when the party of a newly elected president made gains on this scale in Congress were 1932 and 1980; the births of the New Deal and the Reagan Revolution.

So we are about to witness something extraordinary. America, the country that the world loves to think of as an irredeemable hell of gun-toting, government-hating, Bible-clutching, gas-guzzling right wingers, is about to have the most left-wing government in what used to be called the industrialised world.

This week in Canada, voters re-elected a Conservative Government. Canadians, whom most Americans regard as welfare-loving, diversity-promoting, irreligious, gay-embracing peaceniks from the frozen wastes, will soon look on with interest as their neighbours down south experiment, like newly liberated teenagers, with all sorts of weird economic and political substances.

In Europe, Conservatives rule in Germany France and Italy, and despite the miraculous recent apparitions of the Dark Lord Mandelson of the Manipulative Genius and Saint Gordon of Perpetual Financial Succour, the Tories still look likely to take over within the next two years.

Meanwhile, across the Atlantic, a fully Democratic Government will take office with a domestic agenda that would make European hearts pine nostalgically: huge expansion of healthcare; a vast programme of public investment in modern energy technologies; a liberalising social agenda to be pursued, as is now customary, through stacking the courts with politically activist judges.

There's an argument to be made that this sort of revolution is not really what Americans will be choosing in voting for the Democrats. They will be voting against not an ideology, but a record of staggering, almost picturesque government incompetence.

The Bush Administration, despite its image abroad, has not been a paragon of harsh, anti-government individualism. On the contrary, the past eight years have paved the way for big government's return. What has distinguished Republicans is their crass ineptitude in running it.

But that is often how political revolutions are made. A nation isn't suddenly intellectually convinced by an alternative ideology. It just rejects the people who have screwed up, and in doing so, creates an opening for a new era.

It wasn't clear in 1932 that, in electing Franklin Roosevelt, the country was endorsing the New Deal. In fact, as economics student know, FDR campaigned on reducing the government deficit. But that did not alter the magnitude of what followed. And nor, I suspect, will the current occasion for Republican defeat.

A wise old British politician was once asked for a simple explanation of the American political system: “Very simple, “ he said. “It's like our own. They have two political parties. The Republican party is very much like our Conservative party. And the Democratic Party is very much like our... Conservative party”.

No longer. In domestic politics, although perhaps not in international affairs, the Democrats are closer to a European left-of-centre party than any American party in generations. The only difference is that they are about to get their hands on power.

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