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Stephen Colbert outside the window of his office, which overlooks Broadway and his new marquee at the Ed Sullivan Theater. Credit Damon Winter/The New York Times

On a recent Monday night, Stephen Colbert was about as high atop the Ed Sullivan Theater as one can be, looking out over the 200 or so employees of his CBS “Late Show” who had gathered for a roof party as he stood on a staircase with a megaphone in hand.

In a few moments, Mr. Colbert’s bandleader, Jon Batiste, and his fellow musicians would guide the crowd in joyful gyrations while a far-off camera swooped in — all for a few seconds of footage that will appear in the opening credits of this reinvented “Late Show” when it makes its debut on Tuesday.

Throughout the evening, Mr. Colbert had been slipping in and out of the festivities, wearing a steel-blue suit and shimmying with co-workers. Now, from his elevated perch, he was instructing his colleagues on where to stand and how to dance, and he seemed just as comfortable to be in charge of the revelry as he was participating in it.

“Follow the sound of my voice,” he said, its trademark archness reverberating in the warm twilight air. “Go towards the waving man. This is the magic time.”

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Stephen Colbert Credit Damon Winter/The New York Times

Mr. Colbert is approaching his own transformative moment, when he will become the second person to host “The Late Show,” CBS’s marquee late-night franchise, succeeding David Letterman, for whom it was created.

Having spent a decade in the guise of a grandstanding, nominally conservative commentator, this 51-year-old entertainer is preparing for his greatest trick yet. Can he shed the ironist’s mask he wore on “The Colbert Report” and turn himself into the genial master of ceremonies that an 11:35 p.m. network show requires? And can he do it without sacrificing the irreverence and erudition that made his Comedy Central series a welcome antidote to a poisonous political era?

Even as Mr. Colbert has prospered on late-night TV, its landscape has become increasingly competitive in the year and a half since his appointment was announced. He’ll now be expected to hold his own against — if not surpass — friendly rivals like Jimmy Fallon on NBC’s “Tonight Show” and Jimmy Kimmel on ABC’s “Jimmy Kimmel Live,” who have helped break talk shows out of their familiar formats and made viral online content essential to their diet.

Mr. Colbert brings his well-honed political savvy to this crowded marketplace, but he cannot succeed solely with the audience of wonkish young insomniacs who tuned into “The Colbert Report” (which drew about 1.7 million viewers an episode in its last season, according to Comedy Central). He’ll have to broaden his reach, in a way that fits his eclectic, brainy comic taste.

This is the puzzle that Mr. Colbert and his colleagues have been contemplating during their hiatus, even as they feel certain that they have solved it.

If you have been watching closely, they say, the “Stephen Colbert” character who illuminated hypocrisy with a wink and a smirk is not too far removed from the man who will soon appear nightly outside of those quotation marks.

When they started their preparations for “The Late Show,” Mr. Colbert recalled a few weeks ago, “At first, we said: ‘Let’s not take anything for granted. Let’s be willing to throw out everything from the old show.’ And what we’ve discovered is, oh, our sense of humor is our sense of humor.”

The key difference, he added, is that now they can present that sensibility “in a package that is not in mortal combat over the future of our culture.”

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Stephen Colbert with his new desk on the set of “The Late Show.” Credit Damon Winter/The New York Times

As Jon Stewart, the former “Daily Show” host and “Colbert Report” executive producer, said of Mr. Colbert, “What made that character work was the thing that Stephen had to hide, which is his humanity.”

Now, Mr. Stewart said, “Instead of throwing off the cape and revealing the monster, he reveals, actually — oh, this incredibly lovely, talented man.”

Exactly what form his “Late Show” takes is something that will be tinkered with until the moment it hits the airwaves, after a summer Mr. Colbert and his team spent producing original online content without a TV program to broadcast it. As Mr. Colbert said, “You can’t discover the product until you’re making it.”

But once that curtain goes up, Mr. Colbert will be tested on every talent he has developed in a performing career of more than 25 years: not only a singular ability to deflate oversized personalities — including, when necessary, his own — but also a parallel skill set he has been developing behind the scenes, to take command of his work and assert his tastes confidently and unapologetically.

If it happens that the real Mr. Colbert shares a little of his old character’s authoritarian streak, well, how do you think he ended up a television host, anyway?

As he said, in his joking-but-not-really-joking tone: “There’s a degree of narcissism involved in anything in show business. I mean, you can’t do it without a healthy ego. Why would you want anybody to listen to you?”

Operating one July afternoon from temporary offices above a BMW dealership on Manhattan’s West Side, Mr. Colbert had no shortage of works in progress that required his input and approval: a script for an Indian cooking segment needed his review; edits of commercial parodies had to be scrutinized; he had to visit the Ed Sullivan Theater to check on its renovations; he needed a haircut.

Mr. Colbert is keeping many details about his show under wraps until its debut. (When a reporter said that he assumed there would be an opening monologue, he replied: “Really? Are you going to do a monologue?”) But in his taped comedy bits, he continues to present himself as a self-assured if blithely oblivious character, now free to explore the world beyond the daily headlines.

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Mr. Colbert taking in the view of the renovated Ed Sullivan Theater. Credit Damon Winter/The New York Times

Even with no cameras to play to, Mr. Colbert is quick-witted, acerbic and loquacious. He uses words like “catharsis” in casual conversation and can flawlessly pronounce the name of the Mesoamerican deity Quetzalcoatl.

He can also be slightly imperious; as he warned his staff, before departing the office for two weeks of cross-country travels and meetings, “Today is the day for all questions to be answered by me.”

His line of work requires such decisiveness, Mr. Colbert said, not just to navigate the sheer number of choices constantly hurled at him, but because, at its best, a late-night program should be a pure expression of its host and his staff.

“You can make the show into anything you want,” he said. “There is no place for a network to say, ‘This is what it’s going to be.’ Because it’s just the guy and the desk, and he needs around him who he needs.”

Longtime friends and collaborators say that, throughout Mr. Colbert’s many incarnations, his aptitude for on-the-spot innovation has always been in evidence.

Steve Carell, who was a fellow correspondent with Mr. Colbert at “The Daily Show,” said that while almost no one seemed ideally suited for such a structureless job, “it played into his strengths, academically and intellectually — he was creating a world in which he could excel.”

Mr. Carell, who first worked with Mr. Colbert at Chicago’s Second City comedy theater in the 1990s, said that at “The Daily Show,” “We didn’t know what we were doing. We went into the field with some vague idea of what a story would be. And Stephen would go out and create these stories, basically out of very little.”

As a Roman Catholic raised in Charleston, S.C., and a graduate of Northwestern University’s School of Communication, Mr. Colbert did not always mingle easily with other Second City performers.

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Mr. Colbert preparing to film a segment of the show’s opening credits. Credit Damon Winter/The New York Times

As Paul Dinello, who later starred with Mr. Colbert and Amy Sedaris in the Comedy Central shows “Exit 57” and “Strangers With Candy,” described the environment, “It was blue-collar, beer-drinking, college-dropout types.”

“I thought he was a little snooty,” he said of Mr. Colbert, “and I think he thought that I was a half-wit thug.”

Now a “Late Show” supervising producer, Mr. Dinello said that at Second City, Mr. Colbert showed early proficiency for improvising his way through situations and for playing “a high-status idiot.”

“He’s really good at finding the game and being himself at the same time,” Mr. Dinello said. “Once he knows the game, there’s no stopping him.”

On their various projects, Ms. Sedaris said she also recognized in Mr. Colbert what she affectionately described as “the bully-bull-bull, the Taurus in him.”

“He takes charge, and you happily let him take charge,” she said.

That Mr. Colbert would grow into a late-night TV star is not necessarily an outcome Ms. Sedaris said she could have predicted. But, she said, “If it happens for people, at some point, you think, oh, you must, somewhere, have wanted that deep down, right?”

Though “The Colbert Report” is now guaranteed a place in the annals of political satire, its destiny was hardly assured when it had its premiere in 2005. There was little indication then that audiences wanted to see a spinoff of “The Daily Show” or that Comedy Central had the wherewithal to introduce one.

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Mr. Colbert dances with the house band and his staff on the roof of the Ed Sullivan Theater as they film a segment for the show's opening credits. Credit Damon Winter/The New York Times

“For many years,” Mr. Colbert joked, “it was like Comedy Central & Storm-Door Company. I’m not sure how they made their money.”

Through a combination of kismet and current events; a caustic roast of President George W. Bush performed about five feet away from the commander in chief; a series of episodes recorded in Iraq; and a semi-silly Super PAC that created headaches for Comedy Central’s parent company, Viacom, “The Colbert Report” prevailed (and has won six Emmy Awards to date).

There was also a span, about midway through its nine-year run, when Mr. Colbert felt he needed to back away somewhat from its production process.

“It requires an enormous amount of energy, and I thought perhaps I couldn’t sustain it,” he said. “Maybe there were two years where I wasn’t in every morning meeting, and I didn’t like it as much. And then I went right back in.”

Before his most recent contract with Comedy Central expired in December, Mr. Colbert had already decided he would not continue the show.

“I had to change, for my own growth,” he explained, adding that he had “three good ideas” for what he was going to do next, though he declined to describe them. (“If I tell you, somebody else will do it,” he said.)

Mr. Stewart, who was also contemplating whether to stay on with “The Daily Show,” said he and Mr. Colbert often discussed their similar predicaments.

“There were many times where we talked about just doing ‘Rosencrantz and Guildenstern Are Dead’ on Broadway, leaving it all behind and just doing that,” he said.

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Mr. Colbert on the elevator with his ID tag. Credit Damon Winter/The New York Times

More seriously, Mr. Stewart added that in these conversations about the future, he encouraged Mr. Colbert to think about “Late Show” as a plausible next step, being one of the very few candidates who would likely be considered whenever Mr. Letterman decided to step down. But at the time, Mr. Colbert was still grieving the loss of his mother, Lorna, who died in 2013, and still grappling with the daily demands of “The Colbert Report,” while CBS was not dangling any job offers.

Mr. Stewart said: “I think it took him a while to figure out: Can I get excited about this? Can I bring the kind of energy and enthusiasm I’m going to need every day? Because these types of shows use every part of the host, as the ancient Americans would say.”

Sure enough, Mr. Letterman announced in April 2014 that he would retire from “Late Show”; after 22 years, CBS found itself in need of a new anchor for its late-night lineup.

Back in 2002, the network had once courted Mr. Stewart as a potential “Late Show” host, guarding against the possibility that Mr. Letterman might jump to ABC. But this time, CBS had no formal succession plan, according to Leslie Moonves, the president and chief executive of CBS Corporation.

Even so, Mr. Moonves said: “You don’t have to be a rocket scientist to say, ‘All right, who’s out there? Who would you go to if this happened?’ You have your normal list.”

He added: “I know people were clamoring: ‘Well, why don’t they get a woman? Why don’t they get somebody diverse?’ All of which we considered.” But upon learning that Mr. Colbert was available, Mr. Moonves said, “There’s not anything better than that.”

To CBS, Mr. Colbert evoked the best of Mr. Letterman, who Mr. Moonves said was “the smartest guy in the room — it was the thinking man’s thing, and the humor was something that soared.”

And for Mr. Colbert, the thought of succeeding Mr. Letterman — one of his comedic idols, alongside Steve Martin and George Carlin — was irresistible.

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Mr. Colbert going over material with his head writer, Opus Moreschi. Credit Damon Winter/The New York Times

“The only thing that felt like a promotion,” Mr. Colbert said, “was to be offered to take over for Dave.”

(Mr. Stewart, who shares a manager with Mr. Colbert, said he was certain CBS made the right choice. “I’m not suited, and he is,” he said.)

Mr. Colbert is well aware that he represents what he called “the most manila version of America,” as someone who is “a white Christian male, right-handed, brown-eyed.”

“I look, absolutely, like I’m going to sell you insurance,” he said.

And yet, Mr. Colbert said, his outward normalcy disguises a subversive streak. “I’m very comfortable with uncomfortable situations,” he said. “And I think that can seem odd to people, that I like the thrill of discomfort.”

Mr. Moonves said it did not hurt that, just as the 2016 presidential race is heating up, Mr. Colbert was arriving at CBS with a political acumen that would distinguish him from his late-night competitors.

“Frankly, that’s not what Fallon or Kimmel does, particularly,” Mr. Moonves said.

Mr. Colbert is not excising political comedy from his “Late Show”: he has featured Mitt Romney in his early TV commercials, and will host Jeb Bush on his debut broadcast, as demonstrations that Republicans are as welcome to the program as Democrats.

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Mr. Colbert’s “Late Show” office once belonged to David Letterman, whom Mr. Colbert called one of his comedic idols. Credit Damon Winter/The New York Times

But he is thinking differently about how to play with politics on a big-tent show, and acknowledged frustration that on “The Colbert Report,” everything had to be translated “through my character’s ignorance.”

“My show was almost always an argument with someone who wasn’t there,” he said. “I had to be karate-yes or karate-no. I couldn’t be karate-maybe on anything.”

During the Obama years, Mr. Colbert said, the political punditry essentially “yanked the emotional needle in one direction and nailed it there.”

“The story is either ‘transformative president’ or ‘subversive president,’ but that nails you in the same direction, emotionally,” he said. “It’s always either attack or defense, but on one issue. Everything was channeled through the president.”

Now, Mr. Colbert said, “I’m here to play.” Asked what he will do with Mr. Bush, he replied with a laugh, “We’ll do a cooking segment, probably. I don’t know.”

His ascent at CBS has allowed Mr. Colbert a few moments of pure wish fulfillment, like the day this past spring when he quietly paid Mr. Letterman a visit at the Ed Sullivan Theater offices to learn, essentially, how to run “The Late Show.”

“I asked him things like, ‘Where do you stand in the theater?’ ” Mr. Colbert said. “ ‘Where do you talk to your producers?’ He said, ‘No one’s ever asked me these questions before,’ and I said, ‘No one?’ He goes, ‘Who would know to ask?’ ”

Also, Mr. Colbert said, “He showed me how to run the freight elevator.”

(Mr. Letterman declined to comment for this article, but his press representative confirmed Mr. Colbert’s visit.)

On another afternoon in August, Mr. Colbert was moving into the newly redecorated corner office that had once belonged to Mr. Letterman. Among its few furnishings were a Roman soldier’s costume, a Grammy trophy and some Peabody Awards — and a James Bond-style button at Mr. Colbert’s desk that allows him to buzz in visitors without leaving his chair.

While showing off the private wardrobe and dressing room hidden behind his work space, Mr. Colbert said that the self-assuredness in his work was sorely lacking elsewhere in his life.

“I can’t ever decide where I want to eat or what movie to see, where we’ll go on vacation or what clothes to wear — anything,” he said. “But the show, it’s easy. Because I can see it outside of myself.”

Later that day, he and Tom Purcell, an executive producer of the show, gathered in a conference room with some writers to work through another batch of scripts. Mr. Colbert at one point gave a careful explanation of why one particular line should say “the guy” rather than “a guy,” and dismissed another joke about banana bread because, he said, it would be an insult to “the amount of banana bread produced by beautiful, loving members of my family.”

The conversation paused as Mr. Colbert and his staff considered a sketch that began with him addressing his audience directly, and they contemplated the precise language he should use.

An opening greeting like “nation” was too reminiscent of how the host used to speak on “The Colbert Report,” and words like “citizens,” “neighbors” and “friends” felt similarly arch and insincere.

Mr. Colbert hit upon a solution. “How about ‘hi’?” he said. “I like that.”