And then there are the personnel questions. The White House Chief of Staff Rahm Emanuel has already left to run for mayor of Chicago, replaced temporarily by a former Senate staffer. The Secretary of Defence Robert Gates has announced his early 2011 departure. General James Jones (former Marine Corps Commandant and Nato Supreme Commander) resigned as National Security Adviser, after an isolated and failed tenure. Say what you will about Jones's performance, but he was a man of accomplishment. His replacement is another career Democratic staffer. With heavyweight economics advisers such as Christina Romer and former Harvard president Larry Summers already history, can the Treasury Secretary Timothy Geithner be far behind? Do other high-profile officials such as special envoys George Mitchell and Richard Holbrooke really plan to carry on? 

Depending on events in Afghanistan, what of General David Petraeus, the successful leader of Bush's Iraq surge, and Obama's third ground commander in Afghanistan in under two years? Will Petraeus leave the army and stand for President or will Obama name him the next Chairman of the Joint Chiefs of Staff, thus sidetracking a potential political threat? Obama's first team is disappearing, replaced by pale imitations of real players. His lower staffing levels in the White House and State Department are more ideologically hard-core, thus perhaps presaging the more reflexive multilateralism favoured by Obama's enduring European supporters. But for a President in potentially desperate domestic political trouble, kudos from Europeans will mean little. 

The big Washington guessing game is whether Hillary Clinton will leave State, perhaps to challenge Obama for the 2012 Democratic nomination, despite her recent disavowals. Whether she exits or not, Mrs Clinton has not been significant in major Administration decisions and often seems uncomfortable with her portfolio, except for economic and social development issues. Nonetheless, she and her husband remain one of the Democrats' most astute political teams, and their political careers are far from over. 

Amid so much uncertainty, what emerges starkly is the singular importance of Obama the individual. As Harry Truman observed perceptively, the buck always stops with the President. But this presidency rests so much on the uniqueness of Obama — or at least it always has in his mind and that of his most devoted acolytes — that he alone knows the way ahead. And we can therefore be certain that, much as 2010 was a referendum on Obama's policies, 2012 will be a referendum on Obama himself.