That was just one of several ways that Mr. Obama’s campaign operations, some unnoticed by Mr. Romney’s aides in Boston, helped save the president’s candidacy. In Chicago, the campaign recruited a team of behavioral scientists to build an extraordinarily sophisticated database packed with names of millions of undecided voters and potential supporters. The ever-expanding list let the campaign find and register new voters who fit the demographic pattern of Obama backers and methodically track their views through thousands of telephone calls every night.
That allowed the Obama campaign not only to alter the very nature of the electorate, making it younger and less white, but also to create a portrait of shifting voter allegiances. The power of this operation stunned Mr. Romney’s aides on election night, as they saw voters they never even knew existed turn out in places like Osceola County, Fla. “It’s one thing to say you are going to do it; it’s another thing to actually get out there and do it,” said Brian Jones, a senior adviser.
From: this NYT article