The question is which will come the sooner: inauguration or the first claims of betrayal? Barack Obama took wing on the back of imprecise hopes beautifully expressed. But an asset in a campaign can be a liability in office. This is not to repeat the claim that the new president lacks substance or detail - he lacks neither. The experience and intelligence of the team he is assembling shows, on the President-elect's part, great political maturity. He has signalled his will be a centrist administration in which talent will matter more than prior rivalry.

The problem is that the Obama campaign worked on the basis that people projected on to the candidate their own definition of change. The great disillusionment generated by his predecessor melted into a pleasing account of the dawn to come. The Obama texts rarely disclosed much more than the hope that things can only get better. Meanwhile, every vocal supporter has a private definition of success, which will now begin to infiltrate the public debate. As Yogi Berra once said: “You got to be careful if you don't know where you're going, because you might not get there.” The chorus of disapproval is tuning up, off stage left. If the new president is held to the letter of his stated desire for energy independence and serious progress on climate change, he is bound to fall short. It would require an implausible sequence of international co-operation and changes to the habits of the American people to get very far within the limit of a term in office. “Climate is what we expect,” said Mark Twain, “weather is what we get”.

The appointment of Arne Duncan, the reforming chief of the Chicago schools system, shows that Obama's anti-reform campaign stance was a pose to win over the teaching unions, which will now be quick to cry foul. The Democratic primary campaign was also thick with detailed health plans. Every Democrat worth the party card imagines the day when the United States ceases to be the only wealthy industrialised nation that does not have a universal healthcare system. That it manages to spend 16 per cent of GDP not having one is quite a feat. Progress in covering the 47 million people who currently have no health plan will be monitored closely. But progress is likely to be slow. Health reform is exactly the kind of issue on which political capital is spent. It will need the aura of goodwill around President Obama to last.

Hillary Clinton, the new secretary of state, knows only too well the difficulties of health reform. She may not find her new post much easier. US foreign policy is the point at which foreign observers feel permitted to be disappointed too. The international joy at Senator Obama's victory has already brought the world closer together. But, once again, this optimism trails a series of irreconcilable hopes. The real issues of the hour - talking to terrorists, the precarious Middle East, the ambitions of Russia, a strategy for dealing with Iran, a surge in Afghanistan - will require compromise, diplomatic chicanery and, sometimes, at least the threat of belligerence.

Not much of the dirty business of politics was priced into the hope that greeted the election of the president who inherits these problems. Let us hope that judgment does not set in too soon. President Obama may disappoint us, but not yet.