Change, it turns out, wasn't all that it was cracked up to be. Having campaigned for the past year as the agent of transformation, the man who would lead an historic shift in America's political direction, Barack Obama is discovering that there is quite a lot he likes about the way things are.

Since securing the Democratic nomination a few weeks ago, the only change coming from the Illinois senator has been in what he seems to stand for. Last month he dropped his opposition to a Bill before Congress that would give telecoms companies immunity from prosecution for carrying out illegal wiretaps on potential terrorist suspects.

He told a cheering crowd of Israel's supporters of his fervent commitment to the security of the Jewish state and added, for good measure, that an “undivided” Jerusalem should be the nation's capital. He said that he likes free trade after all, and that his primary campaign pledge to dismantle the North American Free Trade Agreement was a case of “overheated rhetoric”.

Last week he expressed support for a Supreme Court decision that struck down a ban on handguns and opposition to another that outlawed the death penalty for rape of a child.

This week he promised to expand President Bush's faith-based organisations initiative, a programme that channels funds to religious groups so that they can deliver social welfare services, which the Left regards as a heinous blurring of Church-State separation.

If next week he named Dick Cheney as his running-mate and revealed that he spends his spare time drilling for oil in wildlife habitats, the only surprise would be that it took him so long.

Of course there's nothing much new in what the senator has done. In the lexicon of modern American politics, it's called a pivot. You campaign hard to the party's extreme in the primary election, where the base voters tend to be. Then, when the nomination is secure and there are no more idealists to be humoured, you pivot back to the centre. The only difference is that in Mr Obama's case the pivot is so hard and so fast that the entire Democratic Party is suffering from whiplash.

A whimper of pain has gone up from the base. Those who really believed in the Audacity of Hope now fear a Timidity of Despair. Thousands of Obama supporters have signed a petition on his website begging him to reconsider his position on the illegal wiretaps - a seemingly minor campaign issue, but one that carries great talismanic symbolism for civil libertarians.

Left-wing commentators have raised the usual cry of betrayal. Arianna Huffington, that rare creature, a young conservative who moved sharply left in middle age, dubbed Mr Obama's move not realpolitik, but “realstupidpolitik”.

Conservatives, meanwhile, led by John McCain's Republican campaign, say that the presumptive Democratic nominee's pivot shows that, for all his talk of offering a new kind of politics, he is really just another cynical politician who will say anything to get elected.

I suspect that all this worries Mr Obama not at all. The louder the Left complains, the deeper the satisfaction at Obama headquarters.

Can you remember a time in, say the past 100 years, when the American people have rejected a presidential candidate because they thought that he was insufficiently left-wing? As for conservatives, they should be cheering Mr Obama, not complaining.

The Left had hoped that 2008 would be a watershed election, a long-awaited counterblast to the Reagan Revolution of 1980 and Newt Gingrich's Contract with America in 1994. And if there were ever a time when the country seemed ready to move left this was surely it. Democrats have a 20-percentage-point lead in opinion polls; those same polls show that almost fourfifths of Americans think the country is on the wrong track. The Republican Party today has all the appeal of a communicable disease.

And yet, on the issues, as Mr Obama understands, people are not so radical. On domestic prosecution of the War on Terror, on cultural issues such as guns and the death penalty, on religion's role in public life, perhaps even on trade and free markets, there is little evidence that Americans are ready to abandon their beliefs.

This is another example of how smart the Obama campaign is. They understand that the biggest impediment to an Obama presidency is lingering doubt about whether their man is a straight-down-the-middle American. Despite having a couple of bestsellers to his name, he is still something of a blank page to most voters, one on which his opponents are trying to doodle all kinds of unflattering portraits of an extremist.

So he is spending these dog days of summer reassuring interested but nervous voters that he is as American as the Fourth of July. And he is doing something else besides - looking ahead to his possible presidency.

A clever pragmatist, he knows that if he wins in November, he will face an overwhelmingly Democratic Congress, clamouring to push the country harder to the left. It would, irony of ironies, fall to President Obama to reassure the American people that he can hold those radical enthusiasms in check.

What is more, by abandoning so many left-wing totems, Mr Obama is emphasising that his promise of change is more than just a swing to the left of the old political pendulum; that his promise of post-partisan politics is a genuine one.

But there is a risk in all this repositioning. Mr Obama will almost certainly have to junk a lot more of the campaign baggage he has accumulated over the past year.

Two big plans look especially vulnerable. The first is his tax policy. This would raise the top marginal rate of federal income tax in the US on those earning $250,000 a year to more than 56 per cent. As the conservative Heritage Foundation pointed out in a report this week, that would put the US somewhere between Finland and Sweden in a league table of marginal tax rates. I doubt whether the American people really want to adopt a Scandinavian economic model, especially during a period of stagnation.

The other challenge is Iraq. Mr Obama continues to insist that Iraq is a failed war and says that he will withdraw all US combat troops within 16 months of taking office. But the closer the election gets, the less plausible it will be to refuse to acknowledge the success that US forces have had in Iraq in the past year.

If, as I suspect is highly likely, he drops these two big remaining planks from his platform, it might not just be the Left who will be wondering: what's left?

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