It makes a difference, according to John Sides:
In 2004, Kim Fridkin and other researchers at Arizona State University showed people footage of the third presidential debate, the debate plus 20 minutes of post-debate commentary on NBC, the debate plus 20 minutes’ time to read commentary onCNN.com. So who won the debate, Bush or Kerry? It depended on whether you watched the news
Erik Voeten follows up:
We should be careful not to suggest that debate performance doesn’t influence the media narrative. It does. But as John’s post notes, the effect of debates filtered by the media will differ from what the effect would have been if it had not been filtered.
The Dish 