File photo of Jay Leno in July 2011 ( Matt Sayles-AP Photo)
's (CMCSA) NBC has denied a report in The Hollywood Reporter that next season could be Jay Leno's last as host of "The Tonight Show" and that he would probably be replaced by comedian Jimmy Fallon.

"We are categorically denying the the reports on a plan for a late-night transition," writes Rebecca Marks, NBC's executive vice president for entertainment publicity, in an email to MSN Money.

Leno, who first took over "The Tonight Show" after Johnny Carson's retirement in 1992, and everyone else at NBC has good reason to be nervous. As my colleague Aimee Picchi recently noted, the network came in fifth in the recent sweeps period, when broadcasters showcase their best programs in the hopes of attracting the biggest audience. Even Spanish-language network Univision did better.

"NBC has certainly had happier times," said Robert Thompson, director of Syracuse University's Bleier Center for Television and Popular Culture, in an interview.

Leno continues to hold his own in the ratings. During the week of Feb. 18-22, "The Tonight Show" was No. 1 with viewers, including those in the 18- to 49-year-old demographic that advertisers love, according to NBC. Leno has delivered bigger 18-to-49 and total audiences than CBS' (CBS) "The Late Show With David Letterman" for 14 straight weeks. He has bested ABC's "Jimmy Kimmel Live" for six out of seven weeks in the target demo and for seven straight weeks in total viewers.

The problem that NBC has is over the long term. The average viewer of late-night shows on the broadcast networks is his or her 50s and is getting older. Compared with cable shows hosted by Conan O'Brien, Jon Stewart and Stephen Colbert, whose audiences are in their 30s and 40s, these viewers are ancient.

For advertisers, younger audiences aren't everything, but they are pretty close. That's where Kimmel, 45, is seen having an edge over more experienced rivals such as 65-year-old Letterman and 62-year-old Leno, which probably worries NBC and gives ABC parent Walt Disney (DIS)cause for optimism.

The NBC late night comedy lineup has had its fair share of drama in recent years. NBC announced in 2004 that Conan O'Brien would succeed Jay Leno as the host of "The Tonight Show" in 2009 only to reverse course the next year and gave the square-jawed comedian his old job back. O'Brien left the network and now hosts a show on TBS.

--Jonathan Berr does not own shares of the listed shares. Follow him on Twitter @jdberr.

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