US Democrats turned to a hero of the past, Bill Clinton, to boost the shaky re-election prospects of Barack Obama, with the popular former president from the prosperous 1990s assuring worried Americans that he feels "with all my heart" that Mr Obama is steering the country to an economic recovery.
Mr Clinton, in a rousing address to a television audience of millions, formally nominated Mr Obama as the Democratic candidate in what is expected to be a tight race for the US presidency against Republican Mitt Romney.
Immediately after Mr Clinton's speech, delegates at the Democratic National Convention made the nomination official in a state-by-state roll call vote.
Mr Obama's acceptance speech later on Thursday will mark the climax of the three-day convention, though Democrats have abandoned plans for Mr Obama to deliver the address at a large football stadium, citing weather concerns.
Democrats have used their convention to push back against Republican claims at their gathering last week that Mr Obama's devotion to big-government solutions has stifled the US economy and swollen the national deficit.
Democrats have countered that Mr Romney would go back to the economic policies that led to a recession, helping the wealthy while harming the poor and middle class.
Mr Clinton, who formally nominated Mr Obama as the Democratic candidate, followed through on the theme.
"If you want a you're-on-your-own, winner-take-all society, you should support the Republican ticket," Mr Clinton said. "If you want a country of shared prosperity and shared responsibility - a we're-all-in-this-together society - you should vote for Barack Obama and (vice president candidate) Joe Biden."
After the speech, Mr Clinton was joined on-stage by Mr Obama, who made his first appearance at the convention. The former president bowed, and Mr Obama pulled him into an embrace as thousands of delegates jammed into the convention hall roared their approval.