David Letterman hosts replacement, Stephen Colbert

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STORY: Stephen Colbert dropped in on David Letterman's late night CBS talk show, the "Late Show" on Tuesday (April 22), to get a glimpse of the rigors of the high-profile job he will take over in 2015. Colbert, 49, who made his mark satirizing political conservatives on his Comedy Central weeknight cable show "The Colbert Report," said on April 10 he would drop his known persona of a dim-witted, big-egoed conservative pundit. There is a measure of risk in abandoning a groundbreaking formula for the comedian whose Emmy-winning show has attracted a strong audience among young viewers, a coveted group that CBS is surely eyeing with its choice of Colbert. But for the comedian who plays the court jester to U.S. politics and is known for inventing zeitgeist catch phrases like "truthiness," he has a chance to distinguish himself against rivals as an expert interviewer, as he has often done on "The Colbert Report", and first as a member of the cast of