CHICAGO » With a "chief scientist" specializing in consumer behavior, an "analytics department" monitoring voter trends, and a geek squad of dozens huddled at computer screens editing video or writing code, the sprawling office complex inside One Prudential Plaza looks like a corporate research and development lab — pingpong table and all.

But it is home to the largely secret engine of President Barack Obama’s re-election campaign, where scores of political strategists, data analysts, corporate marketers and Web producers are sifting through information gleaned from Facebook, voter logs and thousands of in-person visits to reassemble and re-energize the scattered coalition of supporters who swept Obama into the White House four years ago.

Obama has already begun reprising his election-style speeches of 2008, attacking Republicans and defending his record. And his team is ready to begin a major election-year advertising blitz at a moment’s notice as the Republican nominating contest appears to be drawing to a close.

But a huge part of the effort here is dedicated to less flashy yet potentially vital behind-the-scenes work to address some of Obama’s more hidden political challenges.

Many of the small-dollar donors who gave early and often in 2008 have failed to rematerialize, slowing the campaign’s fundraising (though officials say they have no doubt that they will at least raise the $750 million they did then). Some of the volunteers who went to work enlisting friends and neighbors have been turned off by unmet expectations and the hard realities of partisan Washington, though the Republican attacks on Obama this year have helped bring some back into the fray.

And, campaign officials say, they have literally lost track of many reliable Democratic voters, particularly lower-income people who have lost their homes or their jobs or both, and can no longer be reached at the addresses or phone numbers the campaign has on file.

So Obama’s re-election team is sifting through reams of data available through the Internet or fed to it by its hundreds of staff members on the ground in all 50 states, identifying past or potential supporters and donors and testing email and Web-based messages that can entice them back into the fold.

Campaign officials said the Republican fight for the nomination has bought them critical time to develop their campaign machinery. They have been carefully tracking the comments of Mitt Romney, and more recently Rick Santorum, but for now, "that is a side show," Jim Messina, the campaign manager, said in an interview.

The president’s re-election headquarters here look more like a company than a campaign. For the last year, an office that looks nearly as long and as wide as a football field has steadily grown, with more than 300 workers now sitting bunched together. The campaign declines to say how many additional employees are posted in offices across the county, but a payroll of $3 million in January suggests the staff is larger than any ever assembled for a presidential race.

Having spent $48 million already, the campaign invested heavily in its effort to find and reconnect with past donors and volunteers, as well as identify potential supporters, and to entice them all to engage, be it through small donations or volunteering for one of the thousands of neighborhood "teams" the campaign is seeking to build across the nation.

For instance, with the help of Web developers recruited from the private sector, it has dedicated considerable hours creating technology that can make its website fit perfectly onto any screen, be it an iPhone, BlackBerry or Droid — a seemingly small detail that campaign officials say can make a huge difference when it comes to enticing donors or volunteers to stay connected or click a "donate" button.

It has tested various messages sent to different profiles of Internet users to see which gets the best response in terms of commitments of money or time — a single color change, advisers say, can keep an online user on site for longer — with help from personnel including its so-called chief scientist, Rayid Ghani, who joined the campaign last year from Accenture Technology Labs in Chicago.

A review of Ghani’s academic papers during his time at Accenture shows that he specializes in gleaning consumers’ personal interests from available data online, and then developing messages to entice them to buy certain products based on predictive models of human behavior.

"Given the large amounts of data being captured by retailers and the emergence of personal devices that consumers will have access to while shopping in retail stores, the challenge is to create applications and techniques that can learn patterns of behaviors for individual customers and then enable interactions that are highly personalized," read a paper he co-wrote in 2007 entitled, "Data Mining for Individual Consumer Models and Personalized Retail Promotions."

Obama campaign officials declined to describe Ghani’s work in detail. But, in interviews, they said they are intensely studying ways to reach their supporters and to figure out what sorts of messages are most likely to get the best responses.

Officials said they were not indiscriminately scooping up personal data on potential supporters. All of the people they are seeking to contact or tailor messages to, they said, had either provided their email addresses to the campaign or connected with it via its website or social network sites like Facebook.

With 13 million email subscribers as of 2009, more than 12 million Twitter subscribers and some 25 million followers of its Facebook page (compared with, for instance, 1.5 million following Mitt Romney), the campaign has instantaneous access to a huge universe of people, potentially upward of 40 percent of its total 2008 vote count of more than 69 million people, though the campaign refuses to divulge specific numbers.

On top of that, its staff and volunteers around the country are regularly feeding back information from personal contacts they make by phone, email and in person as they seek to understand the voting preferences of people in virtually every neighborhood in the top electoral battlegrounds.

The Obama campaign does not claim to be reinventing the wheel; as in 2008, it is in many ways emulating the 2004 Bush campaign, which had a similar focus on building a volunteer army and highly focused and individualized messages for potential volunteers, donors and voters using personal data. And the Republican Party and its 2012 nominee are certain to employ the same techniques to the degree they have the time and money to catch up.

But the Obama team does claim to be building perhaps the biggest such wheel ever made, with a scale officials called "unprecedented."

Veterans of President George W. Bush’s re-election effort said they did not doubt it, saying there was no comparing the amount of online data and communication available now compared with just six years ago.

"What is new is the power of the Web, the sophistication of what you can do to target people on the Internet, which is 100 percent new and continues to evolve," said Sara Taylor Fagen, a senior strategist in the 2004 Bush campaign who is now a specialist in online advertising and analytics.

Both supporters and critics of the Obama campaign’s approach say it may in the end change the outcome by only a few percentage points. But that, campaign officials said, is enough.

"We’re under no illusions that this is going to be anything but a close race," Messina, the campaign manager, said. "We are preparing for a very close race, as we always have been."