— Arguing that he needs more time to fix the nation's sluggish economy, President Barack Obama formally accepted his party's nomination for a second term Thursday while stressing that voters will face a stark choice in November that could affect their lives for decades to come.

The Democratic incumbent laid out a series of goals for the economy — most of them familiar — and repeatedly said his policies would take middle-class families down a vastly different path than those of his Republican challenger, Mitt Romney.

"The truth is, it will take more than a few years for us to solve challenges that have built up over decades," Obama said. "It will require common effort, shared responsibility, and the kind of bold, persistent experimentation that Franklin Roosevelt pursued during the only crisis worse than this one.

"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," he said.

Above all, the speech was an opportunity for Obama to make his case to millions watching at home how he would use a second term to boost the economy and lower the stubbornly high unemployment that has largely defined the four years of his first term. Returning to a theme he has relied on frequently, the president said his administration is not only addressing the short-term problem, but is looking to build for the future.

The strategy will include federal investments in infrastructure, renewable energy and education, Obama said. The 2008 economic stimulus package he pushed through Congress included billions of dollars in new money for those priorities, but it has been widely criticized by Republicans for not having improved the jobless rate, which has hovered above 8 percent for more than three years.

Obama said he intends to create 1 million new manufacturing jobs in a second term, recruit 100,000 math and science teachers over the next decade and reduce spiraling budget deficits by more than $4 trillion. He provided few details, however, on how his administration would meet those goals.

"If you believe that new plants and factories can dot our landscape; that new energy can power our future; that new schools can provide ladders of opportunity to this nation of dreamers; if you believe in a country where everyone gets a fair shot, and everyone does their fair share, and everyone plays by the same rules, then I need you to vote this November," he said.

The president argued that Romney's proposals for the country — overhauling Medicare, trimming federal spending, halting a looming income tax increase for high earners — would deliver the nation back to the days when former president George W. Bush led a White House so unpopular that many Republicans distanced themselves from it.

Citing severe weather that did not materialize, Democrats moved Obama's speech Thursday from a 65,000-seat outdoor stadium to the smaller, 15,000-seat Time Warner Cable Arena, where most of the convention has taken place this week. The change forced thousands of people who traveled to Charlotte to see the president in person to watch the speech on television instead.

Republicans countered that Obama talked about many of the same ideas in his address that he has been pitching since he was elected. And, they said, those ideas have not worked.

"He offered more promises, but he hasn't kept the promises he made four years ago," Romney campaign manager Matt Rhoades said in a statement. "Americans will hold President Obama accountable for his record — they know they're not better off and that it's time to change direction.."

The end of the political conventions signals the beginning of the general election campaign, when many believe voters will finally start tuning into the race. Polls indicate that the president's ability to win a second term in November will depend in large part on whether he can sell the economic vision for the nation he laid out on Thursday.

"Now, our friends down at Tampa at the Republican convention were more than happy to talk about everything they think is wrong with America, but they didn't have much to say about how they'd make it right," Obama said. "They want your vote, but they don't want you to know their plan. And that's because all they have to offer is the same prescription they've had for the last 30 years."

Political conventions are partly about crafting a message that motivates voters to turn out to the polls on Election Day. But they also are about rewarding longtime volunteers — the party faithful — and encouraging them to spread the word about the presidential nominee.

Obama's address is likely to advance that second goal in a big way, Sen. Ben Cardin said.

"Everyone is going to go back and be a surrogate for President Obama," the Maryland Democrat said. "When someone says President Obama cut Medicare, they're going to be out there saying, 'No, he didn't, and let me tell you what happened.'"

Maryland played a big role at the Democratic convention — five of its elected officials spoke from the podium — but the deeply blue state will not be a factor in the election itself. Both presidential candidates will campaign instead in competitive states such as Florida, Ohio and neighboring Virginia. In 2008, Maryland gave Obama one of his largest margins in the country. He won with 62 percent of the vote.

It's not clear that the Democratic convention or the Republican gathering last week in Tampa will have much of an impact on the underlying dynamics of the race. Polls did not change significantly after the GOP convention, and they continue to reflect a race that is tight and unpredictable. A Gallup poll released Thursday showed Obama ahead by only 1 percentage point, well within its margin of error.