I think it may be possible that this is a case of mistaken causation. Perhaps the daily show tends to attract those who have a somewhat negative view of poiliticians and like this form of satire - just as those who want unabashed conservative bias in their programs are more likely to be attracted to fox news.
I don't think the programs cause the attitudes. I think people's attitudes determine what sort of programming attracts their attention.
I don't believe the participants were necessarily regular viewers of either
The Daily Show or the news.