In the post-FDR era, it’s customary, if not necessarily telling, to assess a newly elected president’s performance after the hundredth day in power, when the electoral mandate dwindles and the honeymoon effect starts to subside. There’s no reason we can’t look at late-night TV hosts through the same lens. Stephen Colbert’s Super PAC won him a Peabody instead of a presidency, but Thursday marked the end of the former “Colbert Report” host’s first 100 days behind the big desk in the Ed Sullivan Theater. And while Colbert has made some concessions to late-night tradition, he’s also staked his claim to the intellectual territory he carved out at Comedy Central. As a consequence, his guests have less glitz and glam than his competitors’, perhaps leading to troubling ratings results.

Leading up to “The Late Show” relaunch on September 8, writers pondered Colbert’s potential to “reinvent late night,” labeled him “the Late Night Hope” and wondered whether highly rated “Tonight Show” host Jimmy Fallon should be scared about a Colbert bump in the night. A few minutes into Colbert’s premiere, though, it was clear there would be no dramatic disruption. All the trappings of late-night TV had returned: the monologue, the obliging bandleader, the fake-cityscape backdrop, the padded chairs that face forward, forcing guests to contort themselves like Tobias Fünke. Colbert was still incisive, still silly and still skilled at improv, but freed of his old alter ego, he seemed restrained, bound to his desk during interviews instead of bounding away to greet his guests and pretend to steal their applause.

But there was something different about the people sitting for those interviews. In his first five shows, Colbert booked an amuse-bouche of big-name actors, including George Clooney and Scarlett Johansson, but he also found room for an author (Stephen King), two politicians (Jeb Bush and Joe Biden), two CEOs (Elon Musk and Travis Kalanick) and a Supreme Court justice (Stephen Breyer). Very quickly, the distinction between late-night shows became clear: If Colbert was for figurative eggheads, Fallon, with his cavalcade of entertainers and athletes, was for people who took the term literally.

Actors remain the lifeblood of late night: They’re well known enough to be dependable draws, and they always have projects to promote. But all-actor episodes have been uncharacteristic of Colbert. A survey of interview segments across Colbert’s first 100 shows — and the 102 for Fallon and 91 for “Jimmy Kimmel Live!” over the same span — reveals that if Colbert hasn’t quite revolutionized late night, he’s at least put his own spin on it, consistent with his higher-brow booking during his first week on air.

SHARE OF HOST’S INTERVIEWS INTERVIEWEE PROFESSION COLBERT FALLON KIMMEL Political figure 11.4% 3.3% 2.2% Writer 9.6 1.4 0.6 Show host 9.2 5.7 6.7 Business figure 6.1 0.0 0.0 Musician 4.4 9.4 6.1 Scientist 3.1 0.0 0.6 Director 2.2 1.9 1.1 Activist 1.7 0.5 0.0 Athlete 1.7 4.7 4.5 Comedian 1.7 3.8 3.4 Artist 1.3 0.0 1.7 Military figure 1.3 0.0 0.6 Model 0.9 0.5 0.0 Religious figure 0.9 0.0 0.0 Astronaut 0.4 0.0 0.0 Chef 0.4 1.9 1.7 Puppet 0.4 0.0 0.6 YouTube star 0.4 0.5 0.0 Animal trainer 0.0 0.5 1.1 Reality star 0.0 0.9 0.6 Late night non-actor guest breakdown

You can read more about how I categorized each guest in the footnotes, but the big finding is that Colbert’s guest list doesn’t look very late night. While his competitors interviewed actors about two-thirds of the time (Kimmel: 68.7 percent; Fallon: 65.1 percent), Colbert’s actor-interview rate lagged well behind, at 42.8 percent. The late-night-guest scene is highly incestuous: Almost 90 guests — roughly 17 percent of all guests interviewed in this period — appeared on at least two of the three shows. But Colbert was much more likely than his late-night rivals to interview writers, political figures, members of the business world, hosts of other shows, scientists and activists. He was also the only host in this sample to interview an astronaut or religious figure.

All three shows share one dubious practice: a pronounced skew toward male guests. Colbert, perhaps mirroring the demographic biases in the fields he tends to mine more heavily, has booked men in 66.4 percent of his segments, which tops Fallon at 61.9 percent and Kimmel at 60.3 percent.

Colbert’s more eclectic mix allows him to showcase his diverse interests, plays to his strengths as an interviewer and sets him apart from his competitors, just as Fallon’s adaptable voice and guitar skills lead him to lean more toward musicians.

It’s not clear, though, that Colbert’s new audience values that variety. Although Colbert continues to outdraw his predecessor, David Letterman, his early buzz died down quickly, as Fallon reestablished his dominance almost immediately after “The Late Show” debuted. Fallon’s lead has grown even larger lately, roughly doubling Colbert’s ratings, which have stagnated at about 680,000 18- to 49-year-olds despite the huge spike he saw in his post-Super Bowl episode. Generating YouTube traffic has proven to be an even higher hurdle for Colbert, the oldest of the three hosts, whose audience is also older, on average, than the competing late-night programs’. That could be because CBS draws an older audience across the board, but it could also be because the financial, political and social leaders Colbert gravitates toward tend to be older than the actors his rivals prefer. Archbishops, theoretical physicists and UN Secretaries-General may make for great conversation, but they’re less likely to play Egg Russian Roulette.

The substance that endeared Colbert to his old audience has survived his transition to CBS. But it could be holding him back on his new, broader stage, and now his first 100 days of audience-building are behind him. “The Late Show” is in no danger of disappearing, but if Colbert wants to take the ratings title in his time slot, he may have to find ways to make viewers more interested in the guests he wants to talk to, or consider catering more to a mainstream crowd.

Thanks to Jessie Barbour for research assistance.

CORRECTION (Feb. 26, 2:45 p.m.): An earlier version of this article misstated the guest list for Colbert’s 100th episode. The actress Krysten Ritter did not appear on the show; she had been scheduled as a guest but was replaced by the musician Graham Nash. The numerical breakdown of Colbert’s guests, showing the percentages of actors, musicians and male guests, has changed as a result, and the numbers have been updated throughout.