Editorial: The US President's new team will forge his legacy

Obama II will not look at all like Obama I – and may not behave like it either

With the swearing-in of the new Congress this week and the re-election of the House Speaker, John Boehner, the complexion of the new US legislature is clear. President Obama can now take the measure of the law-making machine he will have to deal with for the next two years.

And the positive news for him, as for America, is that it is more diverse – in its numbers of women and ethnic minorities – than ever before. Another positive is that it contains fewer "fruitcakes and loonies", to borrow David Cameron's phrase from another context. Candidates from the further reaches of the Tea Party mostly lost last November.

After his tribulations with the last Congress, however, Mr Obama, more than anyone, will know that it is premature to rejoice. The Democrats have increased their presence in the House only marginally. The Republicans keep their majority, while remaining deeply divided, and Mr Boehner's narrow re-election hardly presages more internal cohesion or any greater willingness to meet the President halfway. The fight over budgetary issues is set to resume and could be quite as debilitating next time around.

But the end-of-year brinkmanship that averted the threat of the so-called fiscal cliff, together with the opening of the new session of Congress that followed immediately afterwards, has obscured something else. While there have been changes in Congress that may make Mr Obama's second term a little easier than his first, the bigger, and possibly more significant, changes will be in his own administration. Obama II, it can already be said with confidence, will not look at all like Obama I, and may not behave like it either.

The Treasury Secretary, Tim Geithner, is only the latest of the "big beasts" to announce his intention to leave government. Hillary Clinton had confirmed her plan to leave the State Department long before her recent bout of ill-health. And she is one of the few who has a designated replacement. John Kerry, the Massachusetts senator who was defeated by George Bush for the presidency in 2004, was nominated by Mr Obama just before Christmas and now faces his confirmation hearings.

As well as Treasury and State, Mr Obama also faces gaps at defence – where Leon Panetta is retiring, after being parachuted in to succeed Robert Gates – and at the CIA, following the unexpected resignation of David Petraeus after a sex scandal. There could also be change at the UN, if the US ambassador, Susan Rice, decides to leave, having failed to become Secretary of State.

Of these changes, it is hard to know which is the most significant. Defence, the CIA and State will all be crucial as the US prepares to withdraw from Afghanistan. But it will fall to the next Treasury Secretary to take up Mr Obama's budget battles, while trying to sustain the US economic recovery. Ms Clinton's departure will leave Mr Obama's top line-up exclusively male, unless he promotes a woman, possibly at Defence. In so doing, however, he would rule out the cross-party potential of appointing Chuck Hagel, a Republican, to the role. And however well qualified Mr Kerry may be to become the top US diplomat – his whole career can be seen as preparation for the job – Ms Clinton will be missed not just at State, but more widely. She has given a familiar and authoritative face to the administration that leaves US diplomacy infinitely stronger than it was four years ago.

All these departures present Mr Obama with a challenge. As a second-term president, he will enjoy more room for manoeuvre, even with a recalcitrant Congress, than before. But he will be able to capitalise on his political freedom only if he can fill the looming gaps in his administration with individuals who are equal to the task.