CHARLOTTE, N.C. – President Barack Obama accepted his party’s nomination for a second term Thursday, asking the American people to trust in his leadership in the face of difficult economic times.

Four years after he ran on a lofty message of hope and change, Obama appeared more subdued, more serious and with a sharper edge on a scaled-down convention stage after weather forced a late venue change. He acknowledged times are still difficult for millions of Americans, saying that he was “mindful of my own failings” and that the country has not yet fully recovered from the recession.

“That hope has been tested – by the cost of war, by one of the worst economic crises in history and by political gridlock that’s left us wondering whether it’s still possible to tackle the challenges of our time,” he said before invoking President Franklin Roosevelt and the Great Depression. “But know this, America: Our problems can be solved. Our challenges can be met. The path we offer may be harder, but it leads to a better place.”

In a speech that lasted 38 minutes, the president made only a passing reference to the signature accomplishment of his first term: passing health care reform legislation.

Obama also only mentioned GOP nominee Mitt Romney once by name in the speech, although he offered a general indictment of Republicans as unwilling to say what their plans are to fix the economy and as unable to suggest new ideas.

He said Republicans are offering nothing but more tax cuts for the wealthy at the expense of the middle class.

“Feel a cold coming on? Take two tax cuts, roll back some regulations and call us in the morning!” he quipped.

He zinged Romney as unready to lead.

“My opponent and his running mate are new to foreign policy, but from all that we’ve seen and heard, they want to take us back to an era of blustering and blundering that cost America so dearly,” he said. “You might not be ready for diplomacy with Beijing if you can’t visit the Olympics without insulting our closest ally. “

The president made the case that he has repeatedly made the tough choices – from taking out Osama bin Laden to ending the war in Iraq.

“Four years ago, I promised to end the war in Iraq. We did. I promised to refocus on the terrorists who actually attacked us on 9/11,” he said. “A new tower rises above the New York skyline, al-Qaida is on the path to defeat and Osama bin Laden is dead.”

He made the case for an activist government both at home and abroad, one that invests in energy, education and manufacturing – while also reducing the deficit.

Many of Obama’s policy proposals were recycled from earlier ones that have been rejected by Republicans in Congress, including higher taxes on people earning a yearly income of more than $250,000.

He said he was still eager to reach an agreement on deficit reduction with Republicans but won’t go along with more tax cuts for the wealthy. Nor would he go along with any plan to turn Medicare into a voucher program or to turn Social Security over to Wall Street.

Obama warned that much of what he has accomplished could disappear if he is defeated, but he said he hasn’t given up hope.

“I have never been more hopeful about America. Not because I think I have all the answers. Not because I’m naive about the magnitude of our challenges,” he said. “I’m hopeful because of you.”

Immediately after the speech, Republican National Committee Chairman Reince Priebus released a memo titled “We Can Do Better.”

“In 2008, Barack Obama had no record. His campaign was based solely on words,” Priebus wrote. “This time, words won’t suffice. There’s a clear record, and it’s clear we can do better. ‘Incomplete’ is inadequate,” he said.

Romney campaign manager Matt Rhoades said after the speech that the choice in November would be clear for voters.

“Americans will hold President Obama accountable for his record – they know they’re not better off and that it’s time to change direction,” Rhoades said in a statement.

The GOP also ripped Obama’s promises as recycled ones that he’s already failed to deliver on.

Earlier Thursday, Vice President Joseph Biden delivered a long-winded testimony to the president’s character in his speech.

“This man has courage in his soul, compassion in his heart and a spine of steel,” Biden said.

On the final night here, Biden fully embraced his role as party attack dog, describing in detail two conflicts the president confronted in his first term.

“Because of all the actions he took, because of the calls he made and because of the grit and determination of American workers, and the unparalleled bravery of our special forces, we can now proudly say – Osama bin Laden is dead, and General Motors is alive,” Biden said.

Throughout the last night of the convention, Democratic officials paraded across to the podium to deliver their tailored critiques of Romney. Sen. John Kerry (Mass.) assailed the Republican presidential nominee from his home state for his lack of foreign policy, giving one of the most energetic and blistering critiques of Romney so far.

In another unexpectedly strong performance, former Michigan Gov. Jennifer Granholm roused the crowd with her defense of the auto industry. In a speech filled with fist-pumping and leg-kicking, Granholm struck a populist tone in her depiction of a GOP nominee who does not understand middle-class plight.

“In Mitt Romney’s world, the cars get the elevator and the workers get the shaft,” she said, in what may have been the line of the night.

Shira Toeplitz contributed to this report.