Letterman ends Leno’s brief winning streak

Jay Leno's one-week winning streak is over.

Monday's "Late Show with David Letterman" beat "The Tonight Show with Jay Leno" in adults 18-49 and adults 25-54, the demographic groups that matter most to advertisers. That's according to preliminary fast national Nielsen data just released.

Leno still eked out a win in total viewers, drawing 4.36 million vs. Letterman's 4.19 million.

But in adults 18-49, it was Letterman 1.3/6 and Leno 1.1/5. Among adults 25-54, Letterman notched a 1.6 vs. a 1.4 for Leno.

Leno's "Tonight" reboot had won its first five nights in viewers and demo last week.

But Monday, NBC's primetime average took a big hit, with "Trauma" tanking and "Law & Order" slipping below Leno Monday averages. The lower lead-in resulted in the Leno loss.

(Msnbc.com is a joint venture between Microsoft and NBC Universal.)

It's just one night, of course. And NBC insiders have been insisting that they think it will take months for Leno to regain the regular lead he had over Letterman before the whole Late-Night Mess began.

But the fact that Leno lost to Letterman so soon indicates that any post-Olympics halo is gone.