When Barack Obama stood before the throng in Grant Park on the edge of Lake Michigan in Chicago on that cool night in November four years ago, his wife and two daughters beside him, to declare himself the winner of the race for the White House, he knew he had two acts to follow. One was fairly easy, the other less so.

It was not unhelpful that the man he was replacing, George W Bush, would have historically low approval ratings when the following January he relinquished the keys to the Oval Office. Only less loved was Vice President Dick Cheney. On Mr Bush’s watch, the world’s financial system had been plunged into chaos and the country was in a war in Iraq that had been started on a faulty premise and had proved bloody beyond all expectation.

The much harder act, however, would be his own. Few candidates for president of the United States had generated such a soaring sense of promise as this former Harvard Law Review president, community organiser and state senator from Illinois who had only intruded on to the national consciousness with a gripping speech to the Democratic National convention in 2004, the same year he was elected to the US Senate.

There was of course the fact of his being the first African American to approach the highest office of the land. But that excitement also came for other reasons, including his spell-binding struggle for the party nomination against Hillary Clinton and the wonder of his oratorical skills when crowds of tens of thousands came to see him on the campaign trail.

But there was the small matter of Mr Obama of having promised voters the Earth.  It’s an irresistible trap for a candidate with no record against which those pledges could be compared.  In 2012, his problem – and his rival’s opportunity – is that he does now have a score-sheet for every voter to peruse, and it’s not that pretty.

It is hard to pinpoint when the realities of Washington first took the shine off the Obama West Win. Probably it was happening already in mid-2009 when one of his most treasured goals, the closing of Guantanamo Bay, was already slipping from his grasp. It was obvious by then that his crusade to push through universal health care (or a diluted form of it) and the huge effort put into passing his $787bn economic stimulus bill would leave no spare juice to achieve several other aims, such as passing immigration reform.

Still, Mr Obama’s apple-pie bed was really made in 2010, which began with his declaring that the US economy was in recovery. It wasn’t. Later the same year, the mid-term congressional elections robbed him of a Democratic majority in the House of Representatives amidst the Tea Party wave. Also in 2010, Mr Obama declared this to ABC News: “I’d rather be a really good one-term president than a mediocre two-term president.”

And that, in essence, is the question. Has he been a good one-term president or has he already proved himself mediocre? This is the record voters must judge him on. The answer from the Republicans is unequivocal. After four years of Obama, they assert, Americans are worse off than they were when he came to office. Real take-home incomes are lower, and the world remains in turmoil. As for Mr Obama’s promise to restore partisan civility to Washington, we all know how far he has got with that.

The measure that puts Mr Obama at greatest risk of being ejected from office is joblessness. No president since Franklin Roosevelt has won re-election with unemployment as high as it is now. (There are two more jobs reports before the election that will determine if it budges from the current 8.1 per cent.)

Mr Obama does have achievements to point to. To paraphrase Joe Biden, the Vice President, thanks to his boss General Motors is alive and Osama bin Laden is dead.  He passed the stimulus and healthcare reform acts, he ended the old Don’t Ask, Don’t Tell policy of discrimination against gays in the military and embraced gay marriage, and he ended the war in Iraq and set a timetable for the winding down the conflict in Afghanistan. He helped liberate Libya from a dictator and this year signed an order allowing children of illegal immigrants who study or serve in the military to stay in the country. Some say he has restored America’s standing in the world.

But if he wins a new term, it will in part be because he has been lucky in his opponent. The best the Republicans could come up with to challenge him was Mitt Romney – really?  If an election is ultimately a popularity contest, it isn’t Mr Romney, whose likeability ratings are in the toilet, who wins. It is Mr Obama, who has his share of detractors – even haters – but who still has an ability to connect with the voter, if not quite to thrill the way he used to.

Who's Who in Team Obama

Jim Messina

Until recently, Deputy Chief of Staff at the White House. Now He's in charge of Obama's re-election bid as his campaign manager.

David Axelrod

Soft-spoken ex-journalist who was chief strategist for Obama in 2008 and, later, senior Adviser to his administration. Now senior campaign adviser for the president's re-election big.

David Plouffe

Political strategist (and highly paid public speaker) who was Obama's campaign manager in 2008; now a senior Presidential adviser at the White House. Will play a crucial behind-the-scenes advisory role in the current campaign.

Joe Biden

Brought in to add balance to the Obama ticket. Biden has been a quietly effective, if occasionally undisciplined, vice-president, compared by Obama to a basketball player "who does a bunch of things that don't show up in the stat sheet'.

Michelle Obmama

One of the few unqualified successes of her husband's administration, the popular First Lady will be a vital weapon in the campaign.