The one media platform where the tone of the discourse changed markedly during the last month, and where a candidate managed to generate more positive than negative treatment, however briefly, was in the mainstream news media.
Here, in a sample that also includes cable and talk radio hosts, Romney fared somewhat better during his convention week than Obama during his.
The week of the GOP convention, 36% of the stories about Romney studied in the mainstream media outlets was positive compared with 15% negative-a margin of 21 points. The week of the Democratic gathering, 32% of the stories about Obama were positive compared with 22% negative-a gap of 10 points.
Since then, Obama's coverage has turned somewhat negative, but is still far better than Romney's. In the week following the conclusion of the conventions, September 10-16, 20% of the stories about Obama have been positive compared to 24% negative.
For Romney, the majority of stories (53%) that week were negative. Strikingly, of the 130 stories about Romney examined from the mainstream press that week, researchers found none in which positive assertions about Romney outnumbered negative ones by a ratio of 3-2, the threshold used to determine a story as having a clear tone. But 47% of the stories that week were mixed in tone, meaning that the assertions about Romney were fairly evenly divided.
The mainstream press has also given more attention to Obama during this period, even with the negative publicity associated with Romney's video. From August 27 to September 16, Obama was a bigger newsmaker than Romney, the focus of 667 stories compared with 477 for his rival.  And while the number of stories about Romney exceeded those about Obama by more than 30% during the Republican convention, Obama was the focus on more than twice as many stories as Romney during the Democratic convention.