The Invisible Primary - Invisible No Longer: A First Look at Coverage of the 2008 Presidential Campaign

In the early months of the 2008 presidential campaign, the media had already winnowed the race to mostly five candidates and offered Americans relatively little information about their records or what they would do if elected, according to a comprehensive new study of the election coverage across the media.
The press also gave some candidates measurably more favorable coverage than others. (see link for entire report)