Mike Darnell, a Reality Show Creator, Is Leaving Fox

Fox Overseer of ‘Idol' and Its Kin Will Depart

Not only is “American Idol” expected to lose all four of its judges, it is also bidding adieu to Mike Darnell, the Fox executive who judged correctly at the very beginning that the show would be a hit.

Mike Darnell said he turned down a new contract with Fox.

Mr. Darnell, who has supervised reality programming for Fox since before the term reality show entered the lexicon, said Friday that he was leaving the network at the end of the month.

He oversaw Fox's most popular reality shows (“So You Think You Can Dance,” “MasterChef,” “The X Factor” in addition to “Idol”) and was also its most outlandish innovator (remember “Temptation Island” and “Who Wants to Marry a Multi-Millionaire?”).

Mr. Darnell and his superiors at Fox said that he was offered a new contract but decided to leave. Nonetheless, there was immediate speculation that he was a casualty of the tough television season at Fox, particularly with “American Idol.”

Fox's audiences have fallen by more than 15 percent in the season that ends this month. For “Idol,” once the most popular show on American television, the fall has been steeper. While the slide is not necessarily surprising, since the show has been on for more than a decade, the ratings have been distressing for Fox and its parent company, News Corporation.

When the company reported first-quarter earnings, it said Fox's ad revenue had declined in large part because of the performance of “Idol.” Now the network is contemplating a complete makeover of the show, possibly by replacing last season's judges with a panel of “Idol” alumni like Kelly Clarkson and Jennifer Hudson. Such a move would emphasize the past star-making success of the series.

On Friday there were reports that Ms. Hudson, a finalist on the third season of “Idol,” had signed on for the next season, which will start in January; Fox declined to comment.

Mr. Darnell, in a brief telephone interview, warmly recalled the days when “Idol” drew 30 million viewers a night and acknowledged that it would “never be as big as it once was.”

But no other series will be, either, he added: “I don't think that's possible in television anymore,” with the exception of a few one-time events like the Super Bowl. He expressed confidence about the future of “Idol,” drawing an analogy between it and the 35-year-old “Saturday Night Live” on NBC.

“How many times have you heard that ‘S.N.L.' is dead?” he asked. “Then a new crop comes in and it's a big success again.”

“There's something about these brands,” he said, asserting that “the audience wants to like them.”

Mr. Darnell, whose title is president of alternative entertainment, gained notice in the TV world for his risk-taking and exuberance. But over-the-top reality TV shows are now less the domain of broadcast networks like Fox than of niche cable channels like TLC and A&E. Mr. Darnell has not had a particularly newsworthy show in quite some time. (Franchises he helped birth, however, like “MasterChef,” continue to gain viewers and inspire spinoffs.)

“He brilliantly paved the way for all of us, creating a powerful entertainment genre that audiences can't get enough of,” said Ryan Seacrest, the host of “American Idol.”

Mr. Darnell, 51, joined the network in 1994 as the director of specials; among the most infamous of those was “Alien Autopsy (Fact or Fiction)” in 1995. In 2000, The New York Times called him “the Svengali of sometimes gruesome, sometimes comical specials that took television to new heights - or depths - of perversity.”

Mr. Darnell said he was leaving to pursue other opportunities, without elaborating. Fox executives emphasized that it was his choice. Rupert Murdoch, the chief executive of News Corporation, said in a news release: “Mike took risks at a critical time and was a pioneering force in shaping the reality programming genre that exists today. He's a smart and fearless executive who will be missed.”

Mr. Darnell, asked if his exit was related to “Idol's” ratings weakness, said, “Of course not.”

“Every time my deal comes up, I go through this excruciating decision process,” he said, and this time he concluded he should leave.

“I was able to make this the Wild West,” he said, referring to Fox and its willingness to try stunt shows like “Man vs. Beast” and “World's Scariest Police Chases.”

“But the Wild West has moved,” he added. “Cable, digital, it's everywhere now.”

Putting “Idol” aside, he said his best show was “Joe Millionaire,” the 2003 dating competition that tricked female contestants into believing that the aforementioned Joe was a rich bachelor. Joe was actually a construction worker. About 35 million viewers tuned in for the finale.

A version of this article appeared in print on May 25, 2013, on page B1 of the New York edition with the headline: Fox Overseer Of ‘Idol' And Its Kin Will Depart.