(Adds details on cable competition, paragraph 17)
By Eric Kelsey
LOS ANGELES, April 10 (Reuters) - A new kind of Stephen Colbert will be coming to late-night network television as he succeeds CBS's "Late Show" host David Letterman next year, capping the generational shift in late-night TV's landscape across U.S. networks eager to attract younger viewers and online followings.
Colbert, 49, who made his mark satirizing political conservatives on his Comedy Central weeknight cable show "The Colbert Report," said on Thursday he would drop his known persona of a dim-witted, big-egoed conservative pundit.
"I won't be doing the new show in character, so we'll all get to find out how much of him was me. I'm looking forward to it," Colbert said in a statement.
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.
"A lot of his audience has never seen him as himself," said TV analyst David Bianculli. "He'll bring a lot of that sensibility to it, but it will be a different tone."
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 "The Daily Show with Jon Stewart."
"I think it's smarter than turning it over to someone who has never done the job of interviewing, which he does really well," said Bianculli.
'WE JUMPED AT IT'
Jimmy Fallon, 39, who took over NBC's "The Tonight Show" from Jay Leno in February, and Seth Meyers, Fallon's 40-year-old replacement on the network's "Late Night" program, each developed their comic touch as performers on sketch comedy program "Saturday Night Live."
"Colbert's talent at playfully bantering with guests ... also reflects a contrast with Jimmy Fallon, who despite his knack for musical parodies and viral videos can at times be cloying or empty in the interview format," wrote Brian Lowry, the TV columnist for trade publication Variety.
Details of how the format of "Late Show" will change under Colbert's stewardship, or whether it will remain based in New York City, have yet to be determined.
CBS Entertainment Chairman Nina Tassler said Colbert's representative approached the network about Letterman's spot.
"When his name was brought to our attention, we jumped at it. He stood out above the rest," she said, noting that Letterman gave his blessing.
What is sure is that CBS will be making a play to expand on Colbert's Comedy Central audience and capitalizing on his Twitter following of 6.2 million, which dwarfs the 286,000 at the "Late Show."
Colbert's half-hour show attracts an average of 1.1 million viewers to the Viacom Inc-owned network, according to Nielsen, less than half as many as those who tune into the "Late Show." That number is miniscule in relation to his cultural impact.
Colbert's audience has a median age of 42 years, 16 years younger than Letterman's. Ad sales for "The Colbert Report" rose slightly last year while advertising for "Late Show" declined in 2013, according to ad tracking firm Kantar Media.
Fallon, who has been able to create a strong following on YouTube and has 12.3 million Twitter followers, has lifted the "Tonight" audience by bringing in younger viewers, and attracts twice as many viewers under the age of 50 as Letterman.
The late-night hosts compete for viewers with cable offerings such as the comedy programming on Time Warner Inc's Adult Swim, which draws nearly 1.2 million 18-to 49-year olds on average during the same time slot, according to Nielsen. That's more than either Kimmel or Letterman in the age group most desired by advertisers.
FROM CABLE TO BROADCAST
Unlike his late-night rivals, Colbert has burnished his image by tackling political issues with the biting satire of his self-described "fool" persona.
Although early reaction has been positive to Colbert's hiring, some have wondered if the South Carolina native's backhanded skewering of conservatives - with lines like "reality has a well-known liberal bias" that have made him a favorite on the left - could stand in his way of establishing wide appeal outside of his niche cable personality.
"He's (a) smart and genial fellow who's a good enough actor and improviser to pull off breathtaking satire, but has never spent any appreciable time on camera," wrote Wired's Peter Rubin, adding that audiences may find Colbert's fictional persona preferable to him unfiltered.
But in a signal of how he can connect out of character, Colbert touched viewers last year when he dropped his bloviating persona in a moving tribute to his late mother.
CBS believes he will have enough versatility to work on a broadcast network show.
"He is so nimble, and so smart and quick-witted," Tassler said. "All of those qualities and attributes are a hallmark of a great host." (Additional reporting by Ron Grover and Lisa Richwine; Editing by Mary Milliken, James Dalgleish, Jonathan Oatis and Bernard Orr)