The American people yesterday demonstrated once again their unique capacity for self-renewal by electing the first black man as head of state, not much more than a generation after the country’s African-Americans were accorded full civil rights.

And a mere four years after apparently confirming in place a semi-permanent conservative ascendancy, US voters swept into office a Democratic party that is comfortably to the left of anything the country has seen in the last 30 years.

Yesterday’s results were head-spinning stuff. In electing Barack Obama president by a solid margin, accompanied by a congress with the biggest Democratic majority since the 1970s, Americans have signalled a dramatic change in the direction of the world’s sole superpower.

The country regarded loftily by many Europeans as hopelessly racist and irredeemably right wing has voted to be ruled by a black man, at the head of a party committed to economic redistribution and a foreign policy rooted in peaceful diplomatic engagement.

Two years ago Mr Obama correctly identified that the overwhelming sentiment in this presidential election would be a desire for change.

The Illinois senator embodied — and articulated — the urgency of this desire. The fact that he was a candidate with less experience in national office than any of his opponents in either the Democratic primary or in the general election, was turned from a potential liability into an asset. The colour of his skin, regarded by many pundits as an impossible obstacle to his ambitions, in the end served as the principal guarantee that he was a different kind of leader for a nation in crisis.

America’s yearning for change focused most closely on dissatisfaction with the economy and the wars in Iraq and Afghanistan. John McCain was never able to distance himself from the Republican calamities of the past eight years, even though he had a right to be considered at least as much an agent of change as Mr Obama.

But the desire for a break with the recent past seemed to go much farther. It reflected a broad loss of confidence in the institutions of American leadership. It is not just in Washington that the nation’s leaders are seen to have failed. The collapse of Wall Street has capped a period of mounting anger with what is viewed as corporate greed and cupidity. The internet has unleashed a torrent of angry rebellion against the country’s media and academic establishment. Even the succession of scandals in professional sport, from steroid-injecting baseball stars to bribed basketball officials, has fuelled the popular sense that America has gone seriously off track. With their historic decision yesterday, the American people should certainly get change.

Two questions however hover like a spectre over the celebrations. The first is whether the new president will choose to rein back the economically and socially left-wing agenda of the large Democratic majority in congress.

Though they threw out the Republican party yesterday it is not at all clear that the American people endorsed a Democratic party policy platform that is committed to big tax increases on wealthy Americans and corporations, restrictions on free trade, renewed empowerment of trade unions and the appointment of judges likely to rule in favour of more liberal laws on abortion and gay marriage.

The second challenge is simply the massive task of restoring America’s stature and repairing the damage to the country’s economic power and global political standing.

The country faces challenges on a scale no incoming president has had to tackle since Ronald Reagan was elected in 1980. The economy is in a recession likely to be as deep as the deepest in the last 50 years. Recently, wild financial market mayhem and unprecedented government remedies have fostered doubt in the efficacy of America’s system of economic organisation.

The country’s standing in the world has been compromised by foreign policy failures, the public relations disasters of Guantanamo Bay and Abu Ghraib, and more recently a perceived lack of leadership in the global crisis.

All the while these failings have taken place against a backdrop of steadily mounting fear that the US may be eclipsed within a generation by the emerging powers in Asia.

Remedying any one of these ills would be a tall order for a new president. Trying to cure them all at the same time looks positively Herculean.

President-elect Obama’s first task will be to do whatever government can do to lift the US — and with it the global economy — out of slump. A wide-ranging programme of reform will be necessary to begin to restore trust in the institutions of American leadership – in Washington and in the private sector. Negotiating a responsible drawdown of US troops in Iraq and redoubling efforts in Afghanistan will be essential early steps towards shoring up US national security.

Americans made history yesterday. But the challenges their new leader faces are no less historic.

Times Recommends

• Over the Wall
• Why Africa welcomes the ‘new colonialism’
• Which will come out on top: paper or gold?