Excellent posts down the thread.
But yes, this has been going on for quite some time as Blues said. Take for example, the man voted for decades as the "most trusted man in America", Walter Cronkite. After he retired, he admitted that he was very much a liberal. So we can consider the liberal bias in the media starting back long before even when I realized it, in the 1984 election. How can that be? Quite simply, the bias is not only what is said, it also what is not said, or not reported on at all.
Think of the men who decided what news Americans received in the past 50 or so years, considering the majority of Americans received their national news from the evening newscasts.
NBC: Chet Huntley, David Brinkley, John Chancellor, Tom Brokaw, Roger Mudd, Brian Williams
CBS: Walter Cronkite, Dan Rather, Connie Chung, Bob Shieffer, Katie Couric, Scott Pelley
ABC: Peter Jennings, Bob Young, Frank Reynolds, Howard K Smith, Harry Reasoner, Barbara Walters, Charles Gibson, Dianne Sawyer (and a number of others who were only there for a few months or less)
So, for my lifetime, the majority of the news seen by Americans has been controlled by 20 or so people. Since most people favor one network news over another, that could be as few as five people. Over 50 years! And how many of those people ended up being fairly hardcore liberals? Nearly all, and we just don't know about the rest.
The network news outlets enjoyed absolutely no real competition other than their two competitors until the early 80s, when CNN came along, and they were no real competition. And though they deny it, they claim not to worry about any of the "alternative media" (Fox News, AM radio, and internet).
So in 2008, they pretty much just stopped hiding their bias. Not only the commentators, but the anchors and reporters too. Today, if you watch, what is found in MediaMatters, RightOn, or The Huffington Post today, will be on AP or Reuters tomorrow, and the network news the next day. So half the time they don't even investigate, they just regurgitate the hate-filled drivel generated by the left-wing hate machine.
"I don't think that a society that encourages over a million abortions a year....a society that kills out of convenience, i.e., Jack Kevorkian, can not have consequences." --Rush Limbaugh