Even if debates do matter, there's even less evidence suggesting that the actual candidates' performances do. The media seems to be the far more important player. Arizona's Kim Fridkin and her colleagues conducted an experiment to test this proposition at the 2004 debate in Tempe, Ariz. They asked 74 voters to watch the debate and say who they thought won. 25 watched the debate without seeing commentary afterwards, 25 watched and saw commentary from NBC News which suggested that George W. Bush won, and 24 watched and saw commentary from CNN which suggested that John Kerry won. It turns out that the effects of cable news spin were enormous.

The media even affects how "negative" voters think a debate is. Erik Voeten of Georgetown and the late Lee Siegelman (then at GWU) studied polls asking whether voters in 2000 found the Bush campaign or the Gore campaign more "negative and/or nasty". They found that the first debate had a permanent effect, causing voters to view Gore as more negative. But this was uncorrelated with actual negative statements made by either candidate. This suggests that the media coverage of the debate, rather than Gore's actual statements, lead to this impression.