For "The Tonight Show" and "The Late Show," perhaps the bigger issue is the demographics of who is watching. Jon Stewart of Comedy Central's "The Daily Show" is attracting more viewers aged 18 to 49 – the demographic most sought by advertisers – than is Mr. Leno, and Stephen Colbert, whose "Colbert Report" follows "The Daily Show," is close.
"The Daily Show" has a median viewer age of 43, compared with 58 for "Tonight." (By comparison, the CBS news magazine "60 Minutes," one of the oldest-skewing shows in prime time, has a median viewer age of 61).
That was what moved "Nightline" to its new, later slot. “Nightline” actually has more viewers than “Jimmy Kimmel Live,” but Mr. Kimmel's show generates more than twice the revenue because of its younger audience.
“The lessons are that credible, unbiased, national news is having an increasingly difficult time in reaching an audience large enough to be profitable,” says Richard Goedkoop, professor of communication at La Salle University in Philadelphia.
Though "Nightline" will also get a new, prime time weekly show in prime time Friday, many media experts say the move harbingers the program's slow death.