Earlier this year, NBC News presented a prime-time special on vampires in popular culture, just to promote the same-night premiere of its new Dracula series. I gave that the worst show of the year award on Fresh Air, but at least it was promoting one of its own programs. Tonight, ABC News devotes two hours to an attempt to ride the wave of a popular program from a competitor: PBS’s Downton Abbey. I suppose, though, you can’t blame ABC for not trying to cash in on its own hit shows. I’m not sure it has any.