Michael Calderone points out that, according to the Project for Excellence in Journalism, Delaware Senate Candidate Christine O'Donnell was the most covered candidate of the year:
The amount of coverage shows that the media will focus on a candidate who -- despite little chance of winning -- makes headlines with provocative statements and actions out of character with most mainstream politicians. The media similarly pounced on little-known candidate Alvin Greene after he came out of nowhere to win the South Carolina Democratic primary and began making a series of bizarre comments.
Sure, but Greene didn't draw as much attention as O'Donnell for a couple of reasons, his nomination was a fluke, whereas O'Donnell's nomination was a triumph of ideological purity over political pragmatism. The O'Donnell nomination provided a vivid example of a young, insurgent conservative defeating a moderate, and so provided the media with a microcosm of the larger political media narrative. There were also other factors, some of which were clearly gender-based, that led to O'Donnell getting far more coverage than her relative importance to American politics would have justified.
O'Donnell also isn't further to the right on most of the relevant issues than some other conservative candidates this year, so from a Democratic strategic perspective, the Delaware race, which she was likely to lose anyway, drew attention away from other races where candidates were just as radical.