Outside the convention hall here, volunteers circulated through the crowd at a street festival, hunting for recruits. Want an Obama bumper sticker? They’re free. Just text us with your cellphone number. Inside the hall, giant screens flashed websites and hashtags that delegates could use to connect with the Democratic campaign.

One of the main reasons Barack Obama won four years ago is that he and his team understood the new media environment better than anyone else. They understood that not all voters are equal; that intensity matters; that if you engage people and make them feel part of the campaign, you can unleash a torrent of invaluable energy.

Social media were at the core of this strategy. On the night Obama accepted the Democratic nomination, 85,000 people packed the Denver Broncos football stadium. The price of admission was an email address or cellphone number, and everyone was encouraged to become a broadcaster — to tweet, text, call and email their own networks praising the beatification of St. Barack.

The value of those messages went far beyond the information they contained. The real Obama Revolution was psychological rather than political. That act of communicating turned supporters from passive to active. They moved from the audience to the stage. They now owned a piece of their candidate’s campaign.

Joe Rospars, who helped design the strategy, told the European Business Review that outreach efforts like the convention were primarily about starting a “relationship” with individual volunteers. Today, with the economy in such rough shape, the president is locked in a much closer race. That means Team Obama has to turn out every possible vote, and those relationships Rospars talks about are even more valuable than they were four years ago.

Obama advisers maintain that holding the 2008 convention in Denver helped generate the ticket’s winning margin in Colorado. The same thing will happen this year, they say, in both North Carolina and neighboring Virginia. The relationships started here this week and nurtured all fall through social networks will prove decisive on Election Day.

But Democrats face several huge obstacles, starting with the obvious one: Persistent unemployment and pervasive pessimism make it much harder to generate enthusiasm for the Obama cause. Moreover, Republicans have learned the lessons of 2008 and have borrowed heavily from the Democrats’ insights.

This week, everyone on the Romney email list got a message from vice presidential candidate Paul Ryan with the potent subject line, “Are you better off?” — exactly the question Democrats have trouble answering clearly. The controversy over Obama’s “you didn’t build that” comment was stoked by Romney supporters who “kept a narrative going that wouldn’t have happened without social media,” according to Zac Moffett, Romney’s digital director.

“The Obama campaign has an advantage in that they’ve been doing this for six years and have invested a lot of money in it,” Moffett told Fox News. “But I think every single day we’re catching up, and in some ways we’ve overtaken them.”

Perhaps. But the Pew Research Center reports that Obama “holds a distinct advantage over Mitt Romney in the way his campaign is using digital technology to communicate directly with voters.” During June, Democrats posted four times as much content on twice as many platforms as the Republicans. Team Obama averaged 29 tweets a day to one for the Romney camp; on Facebook, the president had about 27 million followers, compared with 4 million for his challenger.

Within an hour of Clint Eastwood’s confounding performance at the Republican National Convention in Tampa, Fla., the Obama campaign had posted a powerful picture on Twitter and Facebook of the president, taken from behind, presiding over a White House meeting. “This seat’s taken,” said the caption, a message that immediately went viral.

During the Tampa convention, Obama conducted an online chat through the aggregating service Reddit. Many older Americans might think Reddit is an insecticide, or perhaps a cartoon character, but the younger voters in Obama’s target audience know full well what it is and almost crashed the website’s server tuning in. On the opening night here in Charlotte, actor Kal Penn urged young people in the TV audience to go to the website commit.barackobama.com, where they could immediately register to vote. “”You don’t even have to put pants on,” he joked.

Social media will not decide this election. The message is still more important than the medium. But if Obama wins, he can thank the volunteers collecting cellphone numbers on the streets of Charlotte. And the young people, with or without pants, who signed up to vote.

(Steve and Cokie Roberts can be contacted by email at stevecokie@gmail.com)