That's pretty simple enough to answer. It works. This recent article outlines how the President is dominating with strategic online advertising campaigns and buys. He's far out pacing Romney. But what's interesting is HOW the Obama campaign is spending its online advertising.
In 2008 Obama changed the game with online ads. They used the Internet and targeted ads to raise money, and recruit supporters. While their 2012 online ads are geared towards acquisition, the bulk of their spend appears to target specific online audiences with targeted messages. The bulk of their spend is thus used to persuade, not acquire.
In contrast, the Romney campaign, flush with cash, is spending its money with online ads to recruit supporters and raise dollars. Time will tell if they make the shift to be more competitive online with their opponent, and if they move to the persuasion model more than the acquisition model.