The left is quite open about its intentions
I've had occasion to revisit Robert Creamer's rambling political manual, Listen to Your Mother: Stand Up Straight! How Progressives Can Win. He began writing it in federal prison in 2006, and provided a blueprint for Democratic victories in 2008 and beyond.
There is much to take note of--especially as Creamer (a recent ex-con, by the way) is very close to the Chicago cabal around Obama--but a little passage about media bias is worth noting. Creamer calls for the creation of a "progressive echo chamber":
A second way [other than defeat] to demoralize conservative activists is to surround them with the echo chamber of our positions and assumptions. We need to make them feel that they are not mainstream, to make them feel isolated. We need to use the bandwagon effect in reverse...We must isolate them ideologically...
The left is quite clear about its intentions--if you know whom to read and where to look.