Barack Obama is to make a pitch for a second four years in the White House on Thursday night, holding out the prospect of a bold, ambitious and experimental programme to halt American decline on a scale comparable to Franklin Roosevelt's 1930s New Deal.

Obama, at the end of the Democratic convention in Charlotte, North Carolina, is to say the choice on 6 November will be the most important facing Americans for generations, between his own big government approach and the corporate-dominated, small government approach of Republican opponent Mitt Romney.

"When all is said and done – when you pick up that ballot to vote – you will face the clearest choice of any time in a generation," he said in excerpts released in advance of his speech.

"Over the next few years, big decisions will be made in Washington, on jobs and the economy; taxes and deficits; energy and education; war and peace – decisions that will have a huge impact on our lives and our children's lives for decades to come."

The speech was the culmination of a three-day Democratic convention that had an energy largely missing from the Republican one last week. It was more diverse in terms of gender and ethnicity, its delegates more fired up, especially after a powerful speech on Wednesday night by former president Bill Clinton.

Obama, who will be formally nominated by the party as its presidential nominee, builds on Clinton's message that the choice was between who wanted to be part of a "We're all in this together society" or a "Winner take all, you're on your own society".

Obama says: "On every issue, the choice you face won't be just between two candidates or two parties. It will be a choice between two different paths for America. A choice between two fundamentally different visions for the future."

Having made history by becoming America's first black president, he is desperately fighting to ensure his presidency does not end in failure, unable to secure a second term. Polls show a tight race.

One of the biggest criticisms of Obama is that economic recovery has been too slow under his stewardship. He counters that the economy could not be dealt with in just a few years.

The same was true too, he says, of other problems that had developed over generations. His ambition is not just economic recovery and making sure his health care reform is implemented but tackling failing schools and energy dependence.

"I won't pretend the path I'm offering is quick or easy. I never have. 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 for us to solve challenges that have built up over decades," Obama says.

"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. And by the way – those of us who carry on his party's legacy should remember that not every problem can be remedied with another government programme or diktat from Washington."

He adds: "I'm asking you to rally around a set of goals for your country – goals in manufacturing, energy, education, national security, and the deficit; a real, achievable plan that will lead to new jobs, more opportunity, and rebuild this economy on a stronger foundation. That's what we can do in the next four years, and that's why I'm running for a second term as president of the United States."

He promises to create a million new manufacturing jobs by the end of 2016. Mitt Romney has promised 12 million new jobs overall.

He also promises to double exports by the end of 2014 and cut net oil imports in half by 2020.

Even as voters digest Obama's remarks, there will be a sobering moment when the monthly jobs figures are published. Expectations are that they will show more positive news for Obama in previous months, with between 100,000 and 200,000 jobs created, but the overall unemployment rate is expected to remain stubbornly around the 8.3% mark – dangerously high for Obama's re-election chances.

Meanwhile delegates in Charlotte were buoyed by a barnstorming, largely ad-libbed speech on Wednesday night by former president Bill Clinton, who was receiving plaudits from across the US political spectrum. Some Republican strategists went so far as predicting that the speech had handed Obama four more years in the White House.

"I wish to God as a Republican we had someone on our side who had the ability to do that," Steve Schmidt, the Republican strategist who helped run John McCain's campaign against Obama in 2008, told MSNBC.

Another Republican strategist and media commentator, Alex Castellanos, was equally gushing. "This will be the moment that probably re-elected Barack Obama," he told CNN.

A leading Democrat, senator Chuck Schumer, disclosed that Clinton will follow up his speech with a series of campaign appearances on behalf of Obama next month.

The Republicans – who view Americans' anger over unemployment as one of the keys to the White House – are set to pounce on those figures, arguing that the country is worse off now than when Obama became president in January 2009.