Bill Clinton throws his weight behind Obama at convention

Mr Clinton, who oversaw America’s 1990s boom years, was hoping to counter the challenge of Mitt Romney, who still holds a lead among voters as the candidate best qualified to manage the struggling US economic recovery.

Overall, surveys find Americans evenly split on backing Mr Obama or Mr Romney in what looks to be the closest US presidential election in recent memory. While the vastly wealthy Mr Romney is perceived as having an edge on the economy, Mr Obama holds a lead as the candidate seen as best able to relate to the needs of ordinary Americans.

And that was the message brought to the convention hall in Charlotte, North Carolina, by First Lady Michelle Obama on the opening night of the Democratic National Convention.

She declared after nearly four years as president, her husband is still the man who drove a rusty car on their early dates, rescued a coffee table from the rubbish and knows the struggles of everyday Americans because he lived them.

The first lady drew an artful contrast between her husband and Mr Romney without mentioning the Republican’s name, painting a portrait of a leader who knows first-hand the struggles of everyday Americans, who listens to them as president, and who pushes an agenda with their interests in mind.

“That’s the man I see in those quiet moments late at night, hunched over his desk, poring over the letters people have sent him,” she said.

“I see the concern in his eyes ... and I hear the determination in his voice as he tells me, ‘You won’t believe what these folks are going through, Michelle. It’s not right. We’ve got to keep working to fix this. We’ve got so much more to do’.”

The message was echoed during prime television time by San Antonio Mayor Julian Castro, who delivered the high-profile keynote address.

A rising star in the party, Mr Castro is of Mexican-American descent and his selection highlights the importance given to Hispanic voters in the race.

Mr Castro said Mr Obama “knows better than anyone there’s more hard work to do” and told viewers and the audience the country was making progress “despite incredible odds and united Republican opposition”.

He said Republican economic theories have been tested and failed.

With thunderstorms on the horizon, Mr Obama scrapped plans to deliver his acceptance speech at a 74,000-seat outdoor arena. Instead, he was to accept the nomination indoors at the location where the Democratic convention business is being conducted. It holds far fewer people.

Mr Obama is heavily weighed down by more than 42 months of unemployment surpassing eight per cent, the longest such stretch since the end of the Second World War. No president since Franklin Roosevelt in the Great Depression has been re-elected with joblessness so high.

Mr Romney has taken a few days off from the campaign trail, preparing in Vermont for three debates with Mr Obama that could prove pivotal in the close election.

The two conventions have highlighted the contrasting visions of government that voters will face in the November 6 election. Mr Romney’s Republicans, increasingly guided by the anti-tax Tea Party movement, want to minimise the role of government, seen as an obstacle to enterprise and liberty. Mr Obama’s Democrats see government as a force for good, helping the downtrodden and providing education.