David Letterman's Late Show topped the Tonight Show in total viewers over the past two weeks — the first time that's happened since 1998, according to a CBS press release. Also, Letterman continues to make inroads with adults 18 to 34; over the past two weeks, he trailed Tonight in that demographic by the smallest margin since Conan became host. According to NBC's press release, though, Conan is up among viewers 18 to 49, so at least there's that. [TV by the Numbers, DHD]