Dean's the frontrunner so they're doing it to him, mostly, but the press is just picking up right where they left off in 2000 with Gore. It's a sad, sorry, pathetic state of affairs.
Salon has two good articles up. One from Eric Boehlert and one from Aaron Kinney.
Here's a perfect example of a subject for which there is zero need for anonymous sources. Any editor with integrity wouldn't allow them into print.