Jon Stewart mentioned this last night and basically threw it back in O'Reilly's face (O'R said that his viewers were "Stoned slackers")
Too Funny. Lost of info here (actual Annanberg PDF below).
http://www.business-journal.com/NoJokeDailyShowViewersKnowIssues.aspPolling conducted between July 15 and Sept. 19 among 19,013 adults showed that on a six-item political knowledge test people who did not watch any late-night comedy programs in the past week answered 2.62 items correctly, while viewers of Late Night with David Letterman on CBS answered 2.91, viewers of The Tonight Show with Jay Leno answered 2.95, and viewers of The Daily Show with Jon Stewart answered 3.59 items correctly. That meant there was a difference of 16 percentage points between Daily Show viewers and people who did not watch any late-night programming.
The campaign knowledge test covered such topics as which candidate favors allowing workers to invest some of their Social Security contributions in the stock market, the income range at which John Kerry would eliminate the Bush tax cut, and which candidate is a former prosecutor.
Young people who watched The Daily Show scored 48% correct on the campaign knowledge test while young people who did not watch any late-night comedy scored 39% correct. Meanwhile, young people who watched four of more days of network news scored 40% correct, equally frequent cable news viewers 48% correct and newspaper readers 46% correct.
-from July 15 through Sept. 16- Of the 83 political jokes made by Stewart, only 9 specifically targeted Bush. That was 11% of his political jokes. The same number targeted Kerry.
http://www.annenbergpublicpolicycenter.org/naes/2004_03_late-night-knowledge-2_9-21_pr.pdf