Instead of outlining his plans for the country with a rich backdrop of hope and change, as he did in 2008, a more muted and realistic Barack Obama told supporters Thursday night that change couldn't happen overnight and he needed another term to accomplish his goals.

"I won't pretend the path I'm promising is quick or easy, I never have," the U.S. president said to about 15,000 Democrats in Charlotte, N.C.

"You didn't elect me to tell you what you wanted to hear, you elected me to tell you the truth and the truth is it will take more than a few years to solve problems that have built up over decades."

Obama left the cheerleading to his wife Michelle Obama and former president Bill Clinton who both gave rousing speeches earlier this week praising Obama.

CTV's Washington Bureau Chief Paul Workman said Obama presented a realistic view of the grim U.S. economic outlook -- but said progress has been made and called on wavering supporters to hold onto the dreams of change which originally vaulted him into office.

"It was a very sobering view saying look, the country is in serious trouble, it's taken a very serious economic shock and it's going to take a lot of work to get it back to normal. And he asked for four more years to get it done," Workman told CTV's Canada AM on Friday.

Workman said Obama's speech included little substance in terms of policy or plans, but was more of a state of the union-style address that targeted Americans' core values rather than specific plans or issues.

Obama said: "I'm asking you to rally around a set of goals for your country, real, achievable plans that will lead to new jobs, new opportunities that will rebuild this country on a stronger foundation."

The speech was key for Obama, who must win over Democrats who backed him in 2008 but have now wavered in their support as the result of U.S. economic struggles, high unemployment and Obama's failure to come through on key promises such as the closure of Guantanamo Bay.

Obama stayed true to the messaging that has defined his re-election campaign. He said America is recovering, but warned that Republican presidential nominee Mitt Romney would reverse the progress that has been made by reviving failed policies, cutting taxes for the rich and slashing programs that improve the quality of life for ordinary Americans.

Republicans counter that the 8.3 per cent unemployment rate is ample evidence that Obama's policies have failed the country and that Obama's big-government approach has hurt businesses and increased the federal deficit.

Obama and Romney are locked in a tight race that will likely be decided in a few key states. Polls show most Americans see Romney as better equipped to fix the economy, while Obama is the candidate who is more likely to understand the struggles and values or ordinary Americans.

After his speech, Obama was officially approved as the Democratic presidential nominee.

In one of the more emotional and rousing moments of the evening, former congresswoman Gabby Giffords, who was shot in the head in 2011, took to the stage to read the U.S. Pledge of Allegiance -- a moment that had many in tears.