Anyway, this essay at Real Clear Politics gets at the topic and is worth the read. It gets into ideological and partisan "sorting" and all kinds of cool stuff. Highly recommended.
Near the end the author, Jay Cost, cites and agrees with a previous study that argues:
Contemporary American politics is probably best described as polarized on the elite level and increasingly well sorted in the electorate.
Yup. Which leads to all kinds of interesting media content (polarized since media tend to be at the elite level) and a depressed news audience (pissed at elite polarized content?). News networks play to the most polarized in their political coverage, in part because only the polarized are still paying attention to the news, but we get into a chicken-and-egg thing here that I want to explore more on a later post.