There is an emerging bit of scholarly work that suggests those two popular comedy faux news programs -- Jon Stewart's The Daily Show and Stephen Colbert's The Colbert Report -- have very different effects on their audiences.
Stewart's show is more straightforward. He slams Republicans, occasionally Democrats, but basically you know where's coming from. Colbert is more sneaky. He plays a Republican blowhard to make fun of Republicans and blowhards. But his approach confuses some. In other words, he nudges people to like Republicans and those he satirizes, according to one study.
Why mention this? In part the issue is methodological. You wouldn't want to measure exposure to the two programs and then collapse this into a single index called Exposure to Late Night Comedy. There are enough differences, at least suggested in some published studies or a few under consideration at journals, that combining the two might, if not cancel one another out, create measurement error issues. And I think I broke a personal record for the number of commas in a single sentence. Apologies.
Lots of people mention such programs as a source of their news and information, as places that influence what people know. If true, we must be careful in how we take these questions and combine them into a single variable. In fact, best I can tell from some early data, this would be a mistake.