03/18/2010 05:12 am ET | Updated May 25, 2011

Jay Leno Hits New Low, George Lopez Debuts Strong

"The Jay Leno Show" hit a new ratings low Monday night, while the debut of George Lopez's "Lopez Tonight" posted strong and promising numbers.

Leno registered a 1.15 rating in the Adults 18-49 demographic, its lowest A18-49 rating to date, reports the New York Times' Bill Carter. Carter notes that NBC uses the A18-49 metric "to define success because of the number of advertisers who want to reach that group."

Meanwhile, Lopez premiered strong on three Turner networks, averaging 3.2 million total viewers across TNT, TBS, and truTV. The show premiered on all three networks, but will air on TBS, where it averaged 1.7 million total viewers and 1 million A18-49 viewers.

The Hollywood Reporter's James Hibberd says these numbers are promising for Lopez.

"That's higher than the current season averages (though not the premieres) of the adult demo draws for talk shows like CBS' 'Late Late Show With Craig Ferguson,' ABC's 'Jimmy Kimmel Live' and Comedy Central's 'The Daily Show With Jon Stewart,'" Hibberd writes. "If you use the combined three-net number, the show was sampled by more adult demo viewers than Conan O'Brien or David Letterman's average.

In related news, Broadcasting & Cable's Alex Weprin reports that NBC is shaking up the format of Leno's show. Whereas the show had been designed to save "Tonight Show" features like "Headlines" and "Jaywalking" for the end — to keep viewers for the 11PM local newscasts — those features are now following the monologue, almost identical to Leno's "Tonight Show" format.

Watch Lopez's debut monologue:

Watch Leno's Monday night show: