One of the less convincing critiques of the US presidential election campaign, which winds up on Tuesday, is that there has not been much to choose between the incumbent, President Obama, and his challenger, Mitt Romney.

The reality is very different. Instead, a stark choice exists. One can only judge a candidate on his past record and on what he has pledged to do in the future. Romney has said and done a lot of things, many contradictory, some deliberately so. It has been very hard to know during the campaign which Romney is real: the man who backed the precursor of Obamacare when he was governor or the candidate who suggested to donors that almost half of Americans were welfare beneficiaries beyond his political reach? Is he the centrist Republican of the first presidential debate or the man who insisted during the primaries he was "severely conservative"?

Doubts about Romney have accrued not only from his ever shifting politics but also from a wider sense of flakiness. His economic policies have a touch of the fantastic. Romney would enact large tax cuts, reducing revenue, while increasing defence spending sharply, but also arguing he would eat into the deficit by spending cuts alone.

On foreign policy too, Romney represents a return to the disastrous years of George W Bush – threatening confrontation with China by saying he would list it as a currency manipulator, while making bellicose noises about conflict with Iran.

On the other side of the balance sheet, what is there to say about Obama? Few would disagree that America's first black president, who was once able to inspire with his oratory, has lost some of his lustre. The messages of hope and change ran aground in the midst of the worst economic crisis since the Great Depression, exacerbated both by the parlous state of the economy he inherited from his predecessor and by the two huge costly wars he was obliged to fight.

If he has not transformed America in the way that many might have hoped, he has at least mitigated some of the pain while moving to bring to an end one of the US's greatest iniquities, its shocking inequality in affordable healthcare provision. Through the car manufacturers' bailout, his insistence on stress testing of banks and through carefully targeted stimuli, he ensured that the US now appears to be emerging from financial crisis with modest growth and a rise in employment figures even as those European governments that pursued a strategy of austerity are at very best bumping along the bottom. Obama steered a course between the left of his own party, who were advocating for populist but risky measures, and Republican obstructionism.

On foreign policy, the Obama doctrine has been a mixed bag. He strictly limited US involvement in the most significant military adventure launched under his watch, in Libya, and has resisted Israeli pressure for military strikes against Iran. On the Arab Spring, he has preferred by and large to keep a watching brief and avoided an overt entanglement in Syria. After the war in Iraq, launched on a false pretence, and the mishandling of Afghanistan by Bush, this caution should be seen as positive.

But while Obama may have brought an end to some of the human rights abuses of the Bush era, he has failed either to close Guantánamo Bay, as he promised, or moved to end the immunity of Bush-era officials implicated in abuses.

On climate change too, Obama has been disappointing, not least on the campaign trail. In 2008, speaking at the Clinton Global Initiative, he insisted: "No single issue sits at the crossroads of as many currents as energy. This is a security threat, an economic albatross and a moral challenge of our time."

Whoever is elected will face a new presidential term marked by considerable challenges. While the US is recovering from recession it remains weak and would be vulnerable to a number of factors, including a war in the Gulf over Iran disrupting oil supplies, China falling into recession itself or a further worsening of the eurozone crisis.

He will also have to engage quickly with the "fiscal cliff", due at the year's end, when temporary payroll tax cuts are due to come to an end, which promises a tough choice between sharp tax increases for ordinary Americans that would threaten the recovery (but cut the deficit) or an extension of the tax cuts and a consequent increase in the deficit, an issue fraught with political strife.

On the wider stage, the war in Syria is sucking in its neighbours, producing growing instability and, for all Obama's alleged commitment to negotiated solutions, he appears unable to engage Assad's main backer, Russia. The proposed draw down of the majority of US troops in Afghanistan by 2014 and the continuing tensions in Pakistan threaten another crisis.

Despite all of these caveats, the candidate best equipped for the challenging period ahead is Barack Obama. While his campaign has hardly been inspiring, he remains a thoughtful figure who has taken his responsibilities with a seriousness absent from the Bush years. He has brought a new dignity to the White House and while there remain many who are still opposed to him simply for the colour of his skin, for many others he has achieved the remarkable by making it seem unremarkable that the president of the United States is a black man.

His response to hurricane Sandy, praised by both the independent mayor of New York, Michael Bloomberg, and the Republican New Jersey governor, Chris Christie, was a belated reminder that there is a wider middle ground in US politics than the recent period of partisan disputes has often led us to believe.

In the coming months, it will not be solely the new president's responsibility to confront the challenges facing the US and the world but all of those involved in the US political process. Any chance for healing and consensus after the elections should be grasped by all sides. This election offers an opportunity for a fresh start for US politics itself. It should not be squandered.