Jim Bell, the veteran producer who has supervised NBC mainstays ranging from “Today” to its Olympics broadcasts, will leave the company, parting ways after spending a year as the executive in charge of “The Tonight Show Starring Jimmy Fallon.”

“The past year with Jimmy and the terrific team at the show has been a blast, and I will always be grateful for this opportunity,” Bell said in a prepared statement. “But after serious contemplation, I realized I did not want to extend my time at the show. Those thoughts are part of larger ones I have been having about my career, and what has emerged for me is a strong desire to delve into something new — to build on my experience in news, sports, and entertainment so I can broaden and deepen my leadership role in the content universe.”

He will be replaced on an interim basis by Gavin Purcell, a writer and producer who helped launch Fallon’s tenure on “Tonight” and was with him during his time on NBC’s “Late Night,” focusing more heavily on digital and interactive elements of the program. Since that time, Purcell has served as head of media at Vox Media and was the producer in charge of Sarah Silverman’s topical comedy show on Hulu, “I Love You America.” Purcell at this time is not expected to stay in the job permanently.

Bell’s departure comes as “Tonight” a jewel in the NBC lineup that dates back to Jack Paar and Steve Allen, has grappled with the increasing strength of Stephen Colbert’s “Late Show” on CBS. That program has in the last two years thrived on a mix of topical humor, guests from the worlds of politics and media and the host’s never-ending broadsides against President Trump, and is now the most-watched program among the late-night crowd. It has also more recently provided headier competition for viewers between 18 and 49, the audience most desired by advertisers in entertainment programs. Jimmy Kimmel’s late-night show at ABC has also in recent weeks shown new ability to capture that category of viewers.

As Colbert found success riding the Trump-dominated news cycle. Bell used his live-TV expertise to lead the program to produce more spectacles that took “Tonight” away from its usual monologue-sketch-interview rundown. Fallon’s strength has been in shaking up the late-night model , often by finding new ways to interact with celebrities that often go viral. During Bell’s tenure, “Tonight” broadcast from Puerto Rico following its devastation by Hurricane Maria and did an hour-long homage to HBO’s “Larry Sanders Show.” The program opened its current season with five live broadcasts and for the last few weeks even aired originals shows on Sunday following NBC’s “Sunday Night Football,” in an effort to attract some portion of that show’s outsize live audience.

His hire at the show raised some industry eyebrows. Here was a person whose tenure and gravitas at NBC rivaled that of Lorne Michaels, the late-night impresario who has ultimate oversight of “Tonight,” “Late Night With Seth Meyers” and, of course, “Saturday Night Live.” Bell wasn’t just a producer. He is an executive who, like Michaels, managed some of NBC’s biggest businesses. At the same time, NBC’s placement of Bell at “Tonight” no doubt created new dynamics, by taking an executive whose experience was based in news, sports and live events, not comedy. And Fallon has, even in an era when news headlines have pushed new trend in late-night, often avoided talking about current events.

Bell was also supervising NBCUniversal’s coming Olympics production in Tokyo for 2020, and had been involved in any number of facets of that effort. ” We want to thank Jim for his numerous contributions to our NBC Sports and Olympic broadcasts, particularly since becoming the executive producer starting with London in 2012,” said Mark Lazarus, chairman of NBCUniversal’s cable, sports and news assets, and Pete Bevacqua, president of NBC Sports, in a statement. The executives said they “will be making decisions about structural changes to the team in the coming weeks. NBC Sports will likely consider several candidates for the role. Sam Flood, the executive producer of NBC Sports and its cable network NBCSN, is the most senior production executive in the unit, but there are other staffers who would likely be part of a pool of potential successors.

Bell will be the latest in a line of executives at “Tonight” leaving the program. NBC has often attempted to match the host with a business partner who could keep the program’s operations humming, while testing new business models that involve digital media and different experiences based on the show. Fallon’s “Tonight” doesn’t just generate advertising revenue for NBC. Its elements have also been used in creating a new ride at NBC’s parent company’s Universal Orlando theme park and a Ben and Jerry’s line of ice cream.

But the job has not been one for people who crave a long tenure in a single role.When Fallon was set to move to succeed Jay Leno at “Tonight,” his executive producer from “Late Night,” Amy Ozols, was slated to move with him to his new roost. Instead, NBC opted for Josh Lieb, a veteran of “The Daily Show” who had more overall production experience (Ozols has since rejoined Fallon, first as head writer, now as a special projects prodcer). When Lieb left “Tonight” in 2016, a trio of three executives – Katie Hockmeyer, Gerard Bradford and Mike DiCenzo took over. DiCenzo departed when Bell came aboard, and Hockemeyer, after a maternity leave, recently returned as NBC’s executive vice president of late-night programming.

Purcell’s return to the program, however, will likely be greeted with anticipation by show insiders. He was instrumental in the show’s earliest moments in its focus on interactive and social elements, and his return comes at a moment when many of TV’s late-night programs have begun to focus on metrics other than linear audience ratings. In recent weeks, for example, many of the late-night shows have burnished their status on YouTube, where fans can look at individual clips at moments of their own choosing, not necessarily watch an entire “Tonight” broadcast after the late local news.

New audience dynamics have prompted all kinds of new hand-wringing among late-night’s best-known personalities. Conan O’Brien retooled his TBS program earlier this year, cutting it back to thirty minutes from an hour, and placing new emphasis on sketches and bits that might gain traction online. Younger viewers “don’t watch ‘Saturday Night Live’ the way we watch ‘Saturday Night Live,’” O’Brien said while previewing his new efforts in late 2018. Talking to two or three guests and then telling the audience to tune in tomorrow “doesn’t make sense any more.”