In a development that NBC certainly doesn’t need with Conan O’Brien about to mount his late-night comeback on Monday, Jay Leno, who replaced Mr. O’Brien on “The Tonight Show” in January, lost across the board in ratings to CBS’s David Letterman last week.
It was the first time that has happened since Mr. Leno’s return to late night. An express reason that NBC made the move to oust Mr. O’Brien from his spot on “The Tonight Show” was the fear that the show’s perennial late-night leadership was being threatened.
Mr. O’Brien trailed Mr. Letterman consistently last year at this time among total viewers, but he remained ahead or tied most weeks last fall in ratings among the 18-to-49-year-old audience that attracts premium advertising rates. In the same week last year, Mr. O’Brien had a narrow lead of 0.1 rating point in that younger adult group, though he trailed Mr. Letterman by over 1.5 million viewers.
Last week, Mr. Letterman edged past Mr. Leno in every significant ratings category. He had 3.8 million total viewers, to 3.6 million for Mr. Leno, and he scored a 1.0 rating among that 18-49 group to a 0.9 for Mr. Leno. Mr. Letterman was also 0.1 percentage point ahead among viewers ages of 25 to 54.One explanation available to Mr. Leno for falling behind Mr. Letterman may not be easy to turn to because it sounds reminiscent of what Mr. O’Brien’s backers said was the reason for their show’s own ratings struggles last year: NBC’s performance in the 10 p.m. hour.
The discrepancy in audience in the shows at 10 p.m. — which help provide audiences to the late-night shows — was stark. CBS’s shows averaged 11.8 million viewers at 10 p.m. last week, while NBC’s averaged a meager 4.6 million. Among viewers ages 18 to 49, CBS had a big edge as well, with a 2.46 rating to a 1.46 for NBC.
Last year, NBC was performing poorly at 10 as well, but Mr. Leno was the reason then. In the same week last year, his 10 p.m. weeknight show averaged the same 1.46 in the 18-49 measure, but he was attracting slightly more viewers, with five million.
NBC did have an especially low-rated 10 p.m. hour last week because the episode of “Law & Order Los Angeles” on Wednesday was a repeat.
Mr. O’Brien will re-enter the late-night mix at 11 on Monday on the cable channel TBS.