The latest Pew Research survey on the partisan make up cable news network viewership:
CNN: 51% Democrats, 18% Republicans, 23% independents
MSNBC: 45% Democrats, 18% Republicans, 27% independents
Fox News: 33% Democrats, 39% Republicans, 22% independents
It is quite surprising to see that 33% of Democrats watch Fox News. That seems to indicate to me that many viewers can't even differentiate between political messages on cable news. Not good for November.