Barack Obama will have little time to sit back and bask in the achievement of securing a second term in the White House.
After a gruelling and bitterly contested presidential race and a brief moment of euphoria as victory was declared, Mr Obama must immediately return to the struggle with some of the most intractable problems faced by a US president in modern times.
Not least of his difficulties is the challenge of restoring vigour to an American economy which has so far failed to return to convincing health following the financial crash of 2008.
The superpower has yet to recover its mojo after four years with Mr Obama at the helm, with Republican critics blaming the president for sluggish growth, unemployment running at nearly 8%, and sky-high debt. America's economic dominance is also under threat from emerging titans such as China and India, while many of its traditional trading partners - such as Europe and particularly the eurozone - have major troubles of their own.
Many of these problems require long-term structural solutions, and action by other countries - but the president is still likely to take the hit from his public if there is no quick improvement.
The foreign affairs picture is hardly brighter. Managing the withdrawal of troops from Afghanistan by 2014 is a delicate task, and when they depart there is a real danger the nation could slide into civil war. Not only would that mark the 13-year military intervention as a failure, but Pakistan could be further destabilised, setting back efforts to root out extremists.
The stand-off between Iran and the West over its nuclear ambitions has been simmering for years, but there is a sense that the crisis point is approaching. It is still possible that Tehran could back down rather than risk social unrest as sanctions effectively collapse the economy, but the regime may step up development of nuclear weapons, viewing that as the best deterrent to foreign intervention.
Some speculate that Iran could fuel conflicts in Gaza or Lebanon, or carry out its threat to block the key Strait of Hormuz oil route. The newly re-elected US leader will have to weigh up whether and when to take direct action against the rogue state - or alternatively endorse Israeli strikes.
Closer to home, Mexico's escalating war between drugs cartels and the government - estimated by some to have claimed 50,000 lives - has been showing signs of leaking north across the border.
And on top of this is the issue of climate change, which was barely mentioned in the campaign but may come to dominate more and more of the president's time, as experts predict that global warming could mean more extreme weather events like Superstorm Sandy, which devastated New York City in the run-up to polling day.