If most media outlets covering the presidential campaigns had anything to say about it, Facebook, YouTube, blogs, and other social media phenomena would get all the credit for making 2008 the most digital election ever. But that’s only part of the web story. Surely no campaign staffer worth his salt would deny the potential impact of a Barack Obama supporter posting a link on her Facebook page to the candidate’s site. However, the fact is many of the campaigns used a far more measurable online campaign tactic: paid online advertising. As early as January 2007, candidates still in the exploratory stages had begun buying ad space on the Web. Granted, they spent little compared to what they allocated to television...