Broad base, sharp peaks: partisan media leads to increased voter turnout, according to Daily Kos and TPM. I think Kos is right. The key isn't partisan media or not, it's grassroots media or not. It's the distinction between single-channel partisan media and massive activist media. Activism leads to more activism when it's done right.
The evidence is actually quite clear that partisan media are engaging and energizing a new generation of voters, driving participation in our political process higher than before. Aside from the silliness over the "vital center", the fact is people want a choice, and when given one, they are much happier to take part.