According to an article published in The International Journal of Press/Politics, both liberals and conservatives find The Colbert Report funny, but the two groups differ in their perception of Stephen Colbert's actual ideological allegiances.
Additionally, there was no significant difference between the groups in thinking Colbert was funny, but conservatives were more likely to report that Colbert only pretends to be joking and genuinely meant what he said while liberals were more likely to report that Colbert used satire and was not serious when offering political statements. Conservatism also significantly predicted perceptions that Colbert disliked liberalism.
(via cyn-c)