Why? The reason cited by most of those involved in the shows is that a fundamental factor is so far missing in Mr. Obama: There is no comedic “take” on him, nothing easy to turn to for an easy laugh, like allegations of Bill Clinton’s womanizing, or President Bush’s goofy bumbling or Al Gore’s robotic persona… When Mr. Stewart on “The Daily Show” recently tried to joke about Mr. Obama changing his position on campaign financing, for instance, he met with such obvious resistance from the audience, he said, “You know, you’re allowed to laugh at him.” Mr. Stewart said in a telephone interview on Monday, “People have a tendency to react as far as their ideology allows them.”… There is no doubt, several representatives of the late-night shows said, that so far their audiences (and at least some of the shows’ writers) seem to be favorably disposed toward Mr. Obama, to a degree that perhaps leaves them more resistant to jokes about him than those about most previous candidates.