The airwaves are full of the sounds of an election year. Millions of dollars were spent to buy advertisements in Florida. Stephen Colbert flooded South Carolina with Herman Cain ads. Across the country, Newt Gingrich attacks Mitt Romney; Romney attacks Rick Santorum. And Santorum attacks both candidates back.

But amid all the noise, one 2012 presidential candidate is noticeably silent: President Obama. While the Republican candidates duke it out on air, for the moment, Obama’s reelection campaign keeps mostly off television screens. On other screens, however, it’s a different story.

On social media sites, in small surveys, through YouTube videos, the Obama presidential campaign is firing up the base that helped win the White House in 2008. Only this time, thanks to all the available online information about users, the campaign can target voters ever more directly and according to their specific interests.

The Internet did not invent this new way for candidates to target their message. Voter information has always been available to campaigns offline. Candidates know what neighborhoods tend to vote Democratic and which ones are more conservative. Armies of volunteers solicit information, canvassing neighborhoods for clues as to how their candidate fares. Online, however, the campaigns can find far more granular information — and voters themselves supply much of it.

On Obama’s campaign Web site, those with a tendency to care about animal issues out themselves to the campaign by signing a form for “Pet Lovers for Obama.” The campaign can see what links get clicked on: jobs vs. education vs. health care vs. taxes. They might not be able to see where people stand on each issue, but they know what people care most about. The campaign also knows which of its e-mails are read and which ones go unread.

A staff of people monitors the response to campaign messages online, and in the fall, Obama’s campaign staff members hired data scientists to cull more information about its possible supporters.

It’s not just Obama using data research online. Candidates from both parties are monitoring their message across the Web. But compared with the possible Republican presidential candidates, Obama has a huge data pool. More than 12 million people follow his updates on Twitter; more than 25 million do on Facebook. Gingrich has about 1.4 million followers on Twitter, and Romney has about 1.4 million friends on Facebook.

Is this direct campaigning a smart and successful targeting? Is it creating more polarization in an already sharply divided country? Although media focuses on Facebook and Google’s use of data to target ads at consumers, what happens when politicians use similar data sets to target their messages?

Obama’s campaign staff members said that all that data is not gathered to shape the message. They have the message. Rather, they will use the data to determine how the message is delivered. A downloadable ring tone of the president crooning Al Green? A YouTube video touting the the presidential achievements? Or in a graphic shared on Facebook about job creation over the last 23 months?

For the campaign, the goal is to inform the president’s strongest supporters to spread the message, to use technology to talk to the voters as directly as possible and to get their president reelected.

But when a presidential candidate aspires to be the voice of all the voters, what happens when his online strategy speaks to only some of them?