According to NBC’s First Read, the Wisconsin Advertising Project has discovered that contrary to Democrats’ “bed-witting whiners” [note: their terms for themselves], Obama is going negative more than his Republican counterpart:

Campaign ads hitting the airwaves as McCain returned to the road after Minneapolis showed a trend away from positivism, with 77% of ads from the Democratic nominee coding negative, compared to 56% of McCain’s spots.

Obama is more negative, but this not how the press will portray it.