Stephen Colbert will change the face of late night TV on Tuesday, Sept. 8, but perhaps not in the way some viewers expect.

Colbert is only the latest “late-night face-changer” to come along. Both Jimmies — Fallon and Kimmel — were face-changers in their day, so was Conan O’Brien and, oh yeah, so was David Letterman.

That said, they were all known quantities to one extent or another. No one would tag Colbert as an unknown, of course, but what we think we know of him isn’t necessarily what we’ll get when he makes his bow on Tuesday night. He’ll bring new energy to the sub-genre, of course, but in other ways, no one should expect “The Late Show With Stephen Colbert” to completely upend the traditional format of the late-night talk show. No one’s really done that ever on broadcast TV, and it’s unlikely Colbert will either. Genre-busting has always been left to the outliers like Comedy Central (“The Daily Show With Jon Stewart”), FX and FXX (“Totally Biased With W. Kamau Bell”) and even E (“Chelsea Lately”).

To some extent, every successor to Steve Allen, the original “Tonight Show” host, has both changed the face of late night and continued its basic formats and traditions. What made the difference in the success of some hosts and the failure of others was their style and personality.

We knew both Fallon and his “Late Night” follower Seth Meyers from “Saturday Night Live,” so there weren’t really any surprises when they walked out onstage for the first time hosting their own shows. Johnny Carson was a known quantity when he took over “The Tonight Show” in 1962 because he’d hosted game shows; Jay Leno had a thriving stand-up career with lots of TV guests spots before he took over “The Tonight Show.”

But Colbert is different. He’s both a known and unknown quantity. We knew him first from his days as a “Daily Show With Jon Stewart” correspondent, but of course we knew him even better as host of “The Colbert Report” on Comedy Central for nine years.

Losing the persona

All that Comedy Central experience may lead us to think that Colbert is going to shake up late night, but there are two things to consider: First, and most obviously, Colbert played the role of an opinionated uber-conservative talk show host on “The Colbert Report.”

Obviously, we will see the “real” Stephen Colbert when he makes his debut on CBS Tuesday night. He’ll be smart-alecky, lively, energetic, quick-witted and funny. But he will be all of those things without the adapted persona we know so well.

More telling, perhaps, and just a little worrying, is that Colbert is working for the most staid and cautiously strategic of the four major broadcast networks. CBS succeeds by sticking to old formulas. You see it in its entertainment programming, and you see it even more clearly in its news programming. It isn’t a mere coincidence of booking that George Clooney was the first Colbert guest to be announced.

Yes, David Letterman was almost an exception to that generalism in comparison to Leno, whose hosting style was rooted in old-time stand-up and one-liners. But for all his wise-ass-ness, Letterman was always Johnny Carson’s most faithful acolyte, the one and only King of Late Night.

The guest list for Colbert’s first two weeks has a few mildly unexpected names: Supreme Court Justice Stephen Breyer, U.N. Secretary General Ban Ki-moon, Tesla and SpaceX’s Elon Musk and Uber’s Travis Kalanick and, in the musical category, director-choreographer Christopher Wheeldon who will offer a bit from his Broadway adaptation of “An American in Paris” with his two leads.

Those folks are either brainier, artier or tech-hipper than you’d expect to see at 11:35 on network TV.

But other guests are either firmly in the usual suspects category or just outside the door: Stephen King, Jake Gyllenhaal, Naomi Watts, Willie Nelson, Emily Blunt, Scarlett Johansson, Amy Schumer, Lupita Nyong’o. We can probably blame Bill Clinton for making it cool for politicians to do late night, and since it’s election season, Colbert also has Jeb Bush, Sen. Bernie Sanders, and, as a late addition, Vice President Joe Biden, who very well could take the occasion to announce his future plans on Thursday. At least, that’s what CBS is hoping people might think, whether he does or not. Nothing surprising about the pols, though, even Sanders.

Strategic guest list

In other words, this is a very well calculated, highly strategic guest list for Colbert’s first two weeks. It has just the right number of traditional couch-sitters like Clooney, and just the right number of wild cards in a mix that is designed to hold on to traditional late night viewers, who tend to skew older, while not alienating the younger, hipper “Colbert Report” set who will at least tune into the first few episodes to see if there might be reason to continue following him.

In the long run, though, no matter how funny, off the wall and surprising Colbert is, the question is whether he be able to hold onto that younger demographic or will the format itself prove, as it has so often before, too much of an old-school paradigm for younger viewers. After all, a lot of them don’t even watch content on actual televisions.

David Wiegand is the TV critic and an assistant managing editor of The San Francisco Chronicle. E-mail: dwiegand@sfchronicle.com Twitter: @WaitWhat_TV

The Late Show With Stephen Colbert: 11:35 p.m. Tuesday, Sept. 8, on CBS.

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