Folks who have been paying attention should already be aware of this.
The Project for Excellence in Journalism just released the data. See Report from The Daily Kos.
It has been clear for weeks that the media has been attempting to help Hillary Clinton.
And unfortunately if looks like the dirty politics are paying off for Clinton. According to reports, many observers believe that Obama's momentum may have been blunted. Americans tend to respond more to negative politics than to positive politics. So it's no surprise that Clinton decided to go negative. It's the same reason why Republican strategists choose dirty tricks, and lying, over a more positive message.