ABC's former hit show Boston Legal was an Anti Bush mouthpiece as the main character was constantly spewing garbage about the Bush administration which was "counterbalanced" by the rantings of Denny Crain (Shatner). THe clear intent of that show was to make the GOP, corporations, drug makers, gun owners look bad.
NBC's Law and Order was also well known for its leftwing bias-especially after Fred Thompson left the show. Sam Waterson is a well known lefty as was former writer and then producer Mike Chernuchian. On the other hand, some shows were conservative in nature, the most obvious being the long running Chuck Norris series-Walker-Texas Ranger but overall main stream entertainment-tends to lean leftwing in bias. Some of the major cop shows Like the CSI series featuring Gary Sinise (a Republican) or producted by JErry Bruckheimer (a McCain supporter) don't have any real lean.