CHARLOTTE, N.C. — President Barack Obama accepted his party’s nomination for a second term in office and acknowledged slow progress toward solving the nation’s economic woes Thursday night but declared in a Democratic National Convention speech, “Our problems can be solved, our challenges can be met.”

“Yes, our path is harder — but it leads to a better place,” he declared in a prime-time speech to convention delegates and the nation that blended resolve about the challenges ahead with stinging criticism of rival Mitt Romney’s proposals to repair the economy. He acknowledged “my own failings.”

“Four more years,” delegates chanted over and over as the 51-year-old president stepped the podium, noticeably grayer than four years ago when he was a history-making candidate for the White House.

The president’s speech was the final act of a pair of highly scripted national political conventions in as many weeks, and the opening salvo of a two-month drive toward Election Day that pits Obama against Republican rival Romney. The contest is ever tighter for the White House in a dreary season of economic struggle for millions.

Vice President Joe Biden preceded Obama at the convention podium and proclaimed, “America has turned the corner” after experiencing the worst economic crisis since the Great Depression.

Obama didn’t go that far in his own remarks, but he said firmly, “We are not going back, we are moving forward, America.”

With unemployment at 8.3 percent, the president said the task of recovering from the economic disaster of 2008 is exceeded in American history only by the challenge Franklin Delano Roosevelt faced when he took office in 1933.

“It will require common effort, shared responsibility and the kind of bold persistent experimentation” that FDR employed, Obama said.

In an appeal to independent voters who might be considering a vote for Romney, he added that those who carry on Roosevelt’s legacy “should remember that not every problem can be remedied with another government program or dictate from Washington.

He said, “The truth is, it will take more than a few years for us to solve challenges that have built up over the decades.”

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