• by Wayne Friedman , June 25, 2009

With the new late-night battle now in its third week, "The Tonight Show with Conan O'Brien" lost some steam among key viewers, although it maintains its lead over "Late Show with David Letterman."

"Tonight Show" slipped to a Nielsen Media Research 1.3 rating/6 share among 18-49 viewers for the week ending June 19, from a 1.5/6 the week before. That amounts to 1.763 million 18-49 viewers from 2.0 million the week before.

"Late Show" also lost a bit -- down to a 0.8/3 (1.058 million viewers from a 0.9/3 (1.126 million).

But the big news is that "Late Show" beat "Tonight Show" in overall viewers this time around -- 3.5 million to 3.3 million, partly as a result of the attention surrounding the Sarah Palin/Letterman controversy. (ABC's "Nightline had 3.0 million viewers.) The week before, O'Brien had 3.8 million to Letterman's 3.7 million.

Season-to-date numbers still have "The Tonight Show" firmly ahead in total viewers -- 4.6 million viewers to 3.8 million for "Late Show" and "Nightline."

TV advertisers deem specific demographics much more important in their buying decisions than overall viewers. In that regard, 18-49 viewers and 18-34 viewers are important measures for late-night programming.

For younger adults 18-34, Conan again won the week by a big margin -- 930,000 viewers versus Letterman's 352,000. Both shows were down a bit from the week before: O'Brien at 1.040 million, and Letterman with 376,000.

Looking at season-to-date 18-49 numbers, O'Brien has a healthy lead with a 1.8/8, with CBS "Late Show" at 1.0/4 and ABC "Nightline" earning 1.1/4. ABC's "Jimmy Kimmel Live" is posting a 0.6/3, which starts at 12:05 a.m.

In the other new late-night battle, NBC's "Late Night with Jimmy Fallon" has a season-to-date average of 0.8/5 among 18-49 viewers to CBS' "Late Late Show with Craig Ferguson," which has a 0.6/3.