The long transition between a US presidential election and inauguration day is a world away from the same-day flit from No 10 required of an outgoing British Prime Minister. It has its own manners and its own rituals, the first of which – the new first family's tour of the premises – takes place today, when Michelle Obama will be shown around her new home by the departing First Lady, Laura Bush. Meanwhile, incoming and outgoing presidents will confer on matters of state.
Among the most hallowed – and necessary – precepts of the US transition is that the country has only one president at a time. It was invoked by Barack Obama at his first press conference as President-elect, to explain his reticence on policies, such as tax cuts, that he had set out clearly during his campaign. Yet it presents Mr Obama with a problem. Not only is this the first "normal" transition between opposing parties for 16 years – in 2000 the time was sharply curtailed by the "tied" election – but it comes at a time of acute and fast-moving economic crisis.
Convention has it that no controversial or partisan action is taken by an outgoing president during the transition. But there are likely to be times in coming weeks when action needs to be taken, and Mr Bush and Mr Obama take very different approaches to the economy. In sanctioning partial nationalisation of America's major mortgage lenders before the election, Mr Bush narrowed some of the ideological distance. But Mr Obama has somehow to sustain the faith of his voters that he will act briskly on taking office, while not actively undercutting what little authority Mr Bush retains.
It will be a frustrating time, which may be one reason why the President-elect promises early announcements of his cabinet nominations. It may also be why he has set up a new website, capitalising on the success of his internet campaign, to chart progress and solicit views.
But the long transition will be a trying time also for many of those abroad hopeful for changes in US policy. Eight years ago, Bill Clinton put his rapprochement with North Korea on hold after the Republican victory; it has taken the Bush administration eight years to reach almost exactly the same place. In perhaps the single greatest foreign policy disappointment of his presidency, Mr Clinton also ran out of time trying to mediate a settlement in the Middle East. Mr Obama has set as priorities more vigorous engagement in Afghanistan and an end to the US military presence in Iraq. He has also indicated a more multilateral approach to the world generally, raising hopes in Europe. But these are processes where change will be effected gradually; they are also areas where Mr Bush's policy has evolved over the past year and differences may be less marked than many expect.
On two distinct points, however, Mr Obama has promised changes that could transform the international mood almost overnight. He wants to move towards normalising relations with Cuba – investors are already queuing up to move in – and he has spoken of direct talks with Iran. Iran's congratulations to Mr Obama on his victory suggest early interest in Tehran, but already some are voicing disappointment that the next president was so non-committal about Iran at his press conference. They forget that, while the US mood of excitement might have spread around the world, the rules of propriety and power remain in force. Until inauguration day, Mr Obama is little more than a well-protected citizen. The US has only one president at a time.