U.S. President Barack Obama formally accepted the Democratic Party's presidential nomination Thursday night with a 40-minute speech trying to re-ignite the enthusiasm of four years ago.

In sharp contrast to his 2008 speech in Denver, when the keyword was "hope", Obama steered clear of ambitious promises to spell out a "harder but eventually better" second-term vision, just two months ahead of the Nov. 6 showdown.

DO JOB OFFERS WORK?

Who could refuse a job offer during a job crisis? Both the incumbent and the challenger appear to know this well.

When Republican challenger Mitt Romney put up a plan to create 12 million jobs in his first term, Obama asked Americans to be patient with "a real plan," a plan that included job creation goals, such as creating 1 million new manufacturing jobs by the end of 2016.

"I won't pretend the path I'm offering is quick or easy. I never have. You did not elect me to tell you what you want to hear," said Obama in his much-anticipated speech at the party's national convention in this North Carolina city.

"The truth is, it will take more than a few years for us to solve challenges that have built up over decades," he said, in strong contrast to what Romney offered during the Republican party convention a week ago.

"Our path is harder, but it leads to a better place," Obama said.

Obama reminded Americans he led them away from a second Great Depression and warned that Romney's policies would only risk repeating the 2008 disaster.

Both Democrats and Republicans agree the economy remains the top issue on the path to the White House this year. Romney currently still holds a higher rating on the ability to handle the economy, and his fellow Republicans have long been labeling Obama's first-term efforts toward economic recovery and job creation a failure.

Democrats defended Obama's policy, with the best counter-attacks coming not from the president, but the last Democratic two-term president Bill Clinton.

Clinton on Wednesday said it was unfair to blame Obama for the economic ills he inherited from the former Republican government and the trauma he had to face amid the international financial crisis.

"No president, not me, not any of my predecessors, could have fully repaired all the damage that he found in just four years," said Clinton, who had a fabulous economic record.

Noting that many Americans were still "frustrated" by the current fragile economy, he said "too many people do not feel it yet" and that more time was needed for pro-growth measures to take effect.

Clinton touted Obama's efforts across the board, including healthcare reform, education, job creation and economic recovery, issues bearing most of the Republicans' attacks during the election year.

The latest unemployment rate report is due the second day after Obama finished his big moment.

However, a Brookings Institution study predicted the U.S. economic outlook would not improve much, if at all, heading into the November presidential election, with economic growth likely to remain below 2 percent and the jobless rate to linger above 8 percent.

HOW TO CONVINCE THE UNDECIDED

"This is going to be a very hard 60 days until the election," said James Thurber, Director of Center for Congressional and Presidential Studies, American University.

Although there was "very little" Obama could do in terms of changing the economy immediately, Thurber said the incumbent should focus on the battleground swing states, particularly Ohio, Pennsylvania and Michigan, where the economy has been getting better.

Several of the swing states are doing better economically than the country as a whole. For example, Ohio has a 7.2 percent unemployment rate, 1 point below the national average.

"He needs to continue to campaign and to encourage people to support him in those battleground states and he needs to show people symbolically that he is creating jobs by having events where those jobs have been created," Thurber said.

However, one big threat to the president is a late surge by Romney if the domestic economy further weakens in the third quarter. The Brookings study said late-deciding voters "often break for a credible challenger."

Currently, the undecided voters make up from 5 to 12 percent in different polls, depending on whether those leaning in one direction are factored in. "But the truth be told, there are relatively few genuinely undecided voters," said John Zogby, a pollster with Zogby International.