Preferences like these, when cross-referenced with commercial and political data, allow firms to form very detailed pictures of voters.
"We do have models that predict which channels you consume a lot of, if you're a radio listener, what types of music categories would be your likely preference," says Laura Quinn, founder of Catalist, a Democratic communications firm. "I know there's real strong interest in opening up that channel [Pandora] and using it more. That may simply be they're seeing a lot of Republican activity."
Indeed, Republicans seem to be using Pandora more, at least recently. In a unscientific survey of Pandora listeners of both parties conducted by the author, not a single one had heard a Democratic ad. The Romney campaign has been especially active. In addition to display and audio ads, the campaign has taken advantage of one of Pandora's newer offers for political campaigns: E-mail sign-up. Listeners hear an ad from Romney's campaign and are then prompted to allow Pandora to give the campaign your E-mail address.
While research shows Republicans are much more likely to listen to radio, especially country and talk stations, Internet radio appears to be a bipartisan activity. Such a large audience, which can be sorted and picked apart by advertisers, makes Pandora an ideal medium for issue advertising as well.
Over the summer, before the presidential race really began to heat up, one ubiquitous Pandora ad dealt with the "Durbin Amendment" and debit card savings. Paid for by the banking industry's Electronic Payments Coalition, the ad claimed retailers were hoarding money they promised to customers for paying lower fees on debit card swipes. The coalition's making its argument to politicians too--it's spent half a million dollars lobbying Congress and financial regulators so far this year, according to the Center for Responsive Politics.
As more people avoid the most effective political medium, television commercials, by using DVR, tablets, and smartphones, Internet radio listeners should expect a political Pandora even after this fall's election.
Seth Cline is a reporter with U.S. News and World Report. Contact him at firstname.lastname@example.org or follow him on Twitter.