Conan O’Brien and David Letterman continue to duke it out in the late night ratings arena, with Letterman regaining the households lead and O’Brien dominating in the financially vital key demographics.

In Nielsen’s overnight metered-market households, Letterman regained the lead with a 3.5/8 to O’Brien’s 3.0/7. Letterman’s number was no doubt boosted by intense media coverage of his recent remarks about Alaska Gov. Sarah Palin.

The 11:35 p.m. picture is much different when looking at demo information, the currency most advertisers use when determining their buys.

Perhaps tired of media reports about Letterman beating O’Brien in the overnight household numbers, NBC has begun distributing data from Nielsen’s 21 local markets with people meters to boost its claim that O’Brien is actually attracting a much younger audience than Letterman.

And by that standard, O’Brien’s "Tonight Show" (1.5/6) easily beat Letterman’s "Late Show" (0.9/3), winning by a wide 67 percent margin.

Overnight demos for late night aren’t usually considered all that reliable, but NBC tracked the overnight demos for O’Brien’s first week as host and found that they compared favorably to final national demos released yesterday. Rather than let household numbers shape the media portrait of the late night race, NBC has clearly decided to fight back with demo data.

Meanwhile, the Pentagon is expected to announce the first wave of casualty reports from the War on Late Night as soon as next week.

And, yes, Gov. Palin, that was a joke. We are not mocking the brave men and women of our armed forces. But if you’d like to attack TV MoJoe for doing so, we’ll gladly take the attention.

That is all.