The US is the most powerful nation on earth, but its position of global supremacy is being challenged - economically, militarily and politically. And the person many Americans hold responsible for these failings is the president who promised them change. The worldwide economic crisis of 2008 started in the US and the aftershocks are still being felt today. Unemployment is running at more than eight per cent, productivity is down and the national debt is a whopping $137bn. Such turmoil makes it hard to honour electoral promises. The country is deeply divided. The machinery of government has been tied in knots by partisan bickering and the rise of the right-wing, anti-state Tea Party and the street protests of the left-wing Occupy Wall Street movement are a reminder of how polarised the nation has become. Despite this, Barack Obama, the US president, has pushed through healthcare reform and turned around the failing auto industry. He has stopped the war in Iraq and killed Osama bin Laden. But is this enough to win re-election for a second term? And, whoever wins, will the next president have the unenviable task of overseeing the US' decline?