|Former US President Bill Clinton delivers a speech at the Democratic convention [Photo:BBC]|
His 50-minute speech at the Democratic convention in Charlotte, North Carolina, was strongly critical of Republican economic plans.
He launched a full-throated defence of Mr Obama's policies, saying his economic policies were working.
Mr Obama will take on Republican Mitt Romney in November's election.
Bill Clinton's speech is being seen as the high point of a revitalised relationship between the two presidents and as an attempt to boost Mr Obama's appeal with white working-class voters.
Polls show these traditional Democratic voters are wary of Mr Obama, but Mr Clinton has a strong record in winning their support.
Mr Clinton told the crowd that they would "decide what kind of country you want to live in".
"If you want a 'you're on your own, winner take all society' you should support the Republican ticket," he said. "If you want a country of shared opportunities and shared responsibilities - a 'we're all in it together' society - you should vote for Barack Obama and Joe Biden."
Mr Clinton attacked Republicans for blocking further progress on the economic recovery and getting deep into the detail of policy debates.
"In order to look like an acceptable, moderate alternative to President Obama, they couldn't say much about the ideas they have offered over the last two years," he said, referring to the Republican convention in Florida a week ago.
Reminding the crowd that Senate Republican leader Mitch McConnell had revealed that their number one priority was to get Mr Obama out of office, he declared: "We're going to keep President Obama on the job."