As Democrats head to North Carolina this weekend for their national convention, one concern for President Obama’s campaign advisers is whether Charlotte can do for them in 2012 what Denver did in 2008.

Can they use their convention to help win the battleground state hosting it?

Rather than utilizing the convention simply to anoint the nominee, Democrats hope to deploy it as a organizing vehicle in North Carolina.

Four years ago, Obama’s team used the Denver convention to assemble a grass-roots army of thousands that was widely credited with helping him win Colorado, a battleground state that propelled him to victory against Sen. John McCain (R-Ariz.). They packed Invesco Field the night Obama spoke with a record convention crowd of more than 84,000 — but only after taking many of their names and e-mail addresses and asking them to help for the duration of the campaign.

Whether Obama can amass a similar army in Charlotte could determine his fate in North Carolina and nationally in November. The president’s field operation — a network of offices and on-the-ground staffers, along with volunteers focused on registering voters and turning them out on Nov. 6 — is widely viewed as one of his leading advantages against his Republican challenger, Mitt Romney. But it is hard to judge the effectiveness of the operation until the convention, when the army will either assemble or it won’t.

Steve Kerrigan, the chief executive of the Democratic convention, said holding a convention in a swing state does not automatically swing that state in your candidate’s direction. “It’s how you use it,” he said.

“There were 44 Democratic conventions before the Denver convention,” Kerrigan said. “We lost 22 states that hosted us and we won 22 states. It was an even split because we used the convention as a nominating tool, and then we moved on.”

That changed dramatically in 2008, when 25,000 volunteers were signed up at Invesco Field. The rest, Kerrigan said, is history.

“We think the Colorado model is a useful model, a useful benchmark,” said Jim Messina, Obama campaign manager.

Locked in a much tighter race this time, Obama is investing more heavily in state-level organizations than he did four years ago. In North Carolina, that means 47 offices and a staff of dozens coordinating phone banks, door-knocking expeditions and neighborhood parties meant to rally voters to action.

It also means a convention focused less on introducing the president and more on engaging his troops and the public. There is an outdoor street festival on Labor Day open to anyone. One of the key themes of the convention will be inclusion and community service, meant to connect with a broad range of Democrats, and a final day of speeches at a huge outdoor stadium where tens of thousands of seats will be made available to the public, not just delegates.

Romney and his allies, in contrast, are spending much more of their money on the airwaves, bombarding North Carolinians with television ads rather than trying to match Obama’s field operation on the ground. And in Tampa, where the Republicans just held their convention, the biggest public event was a party thrown by Rep. Ron Paul’s insurgent campaign.

“Our campaign has build a formidable ground game that will be able to go toe to toe with President Obama’s machine,” Romney spokesman Ryan Williams said. “We have invested our resources wisely, placed our assets strategically and are confident that we have an effort in place that will turn out our vote in November.”

But one sign that Obama’s organization is paying dividends in North Carolina is in voter registration, where the Democratic advantage has grown more than in any other state. According to state election statistics, Democrats have registered more than 30,000 new voters this month, compared with 23,000 for Republicans. Additionally, the number of Hispanic voters has nearly doubled since 2008, to 97,000.

One hint of Obama’s organizational strength in North Carolina is the number of volunteers who have qualified for a free ticket to the final day of the Charlotte convention, when Obama and Vice President Biden will speak and when events will move from an indoor arena into the outdoor, 74,000-seat Bank of America Stadium.

Several months ago, the campaign launched what it calls its “9-3-1” program, which promised “one ticket” to anyone who volunteered nine hours and three shifts on the campaign. As of this week, more than 6,000 North Carolinians had qualified for a ticket. In other words, activists have given the campaign more than 50,000 volunteer hours on the ground in North Carolina. After Labor Day, that grass-roots activity is expected to tick upward even more.

“The line was wrapped around the building,” said Charlotte Mayor Anthony Foxx, who saw hundreds of volunteers show up to claim their tickets at one downtown office Thursday, the first day they could. “It was incredible.”

Jonette “Jo” Harper, 45, who lives in Huntersville, a Charlotte suburb, got one of those tickets. She gives the Obama campaign between 10 and 30 hours per week, most if it calling potential voters from her home. Harper, who also volunteered in 2008, said she and many of her friends and relatives are as motivated this year as they were four years ago.

“People are so excited that the president is coming,” she said. “Everyone I know will go to the convention.”

Still, such enthusiasm has not eased the apprehension among campaign aides about whether Obama will be able to fill the outdoor stadium. He has not drawn the huge crowds this year that were commonplace 2008.

Rain is threatening for much of this week and could make it that much more difficult for Democrats to fill seats Thursday. Convention organizers said the final night of speeches will take place at the stadium rain or shine. There is a contingency plan in place in the event of severe weather, but officials said that such plans would be announced closer to the date if the need arises.

Another consideration is security, which is much more challenging this time because Obama is now the president. Screening tens of thousands of supporters is difficult and sometimes impossible, depending on the venue. But they are going to try.

“This is a very important tool for us to get more people into this campaign,” Messina said.