We already knew that a significant number of people over the age of 49 defected from the Jay Leno–hosted version of NBC's Tonight Show to their fellow baby boomer David Letterman's Late Show program on CBS after Conan took the reins in June, but now it seems like O'Brien's supposed fortress of support within Gen X and Gen Y circles seems to be eroding with every passing week. According to a CBS press release that Vulture buddy Nikki Finke got her hands on, last week's run of Tonight Show episodes was the lowest rated since Letterman's first week as host of the Late Show way back in 1993. But if you believe the spin that's been coming out of Jeff Zucker's mouth since the transition, overall ratings don't really matter to NBC, as they're more concerned about the ratings in their coveted 18-to-49 bracket.
Unfortunately for NBC, things aren't going so well for them in that department, either. Not only has Dave basically pulled even in the 25-to-54 race, but Conan's ratings in the 18-to-34 segment have dropped almost one full point since he took over on June 1. One thing's for certain: The two months and change before Jay Leno comes back into the NBC fray in mid-September is going to be a white-knuckle ride for the network. We don't anticipate anyone over at NBC hitting the panic switch and making any rash moves until the end of the year, but you can bet that Jeff Zucker is already dreading his year-end review.