There's an excellent profile of Jon Stewart, host of the Daily Show on More4, in today's Observer by David Smith (http://www.guardian.co.uk/media/2008/sep/14/television.television ).
Describing one recent sketch on the show, Smith writes:
"Showing politicians condemn themselves out of their own mouths is a classic Stewart manoevre. In one sequence, the Daily Show spliced excerpts from McCain's acceptance speech at the Republican convention with one by Bush before he became president. The word-for-word similarities were uncanny, promising change in Washington, a pro-life culture and the rest. It was a masterpiece of editing that required no narrative to tear down false idols, arguably more effective than anything the Democrats have thrown at McCain in recent weeks. It makes Obama's argument that McCain represents a third term of Bush more eloquently than the candidate himself has so far managed."
The article also notes that the rest of the US media were forced to follow the Daily Show's exposure of Dick Cheney's links to Haliburton & the awarding of multi-million dollar wartime contracts to the firm.