Letterman narrows late-night ratings gap with Leno LOS ANGELES (Reuters) - Rival talk show hosts Jay Leno and David Letterman are fighting again, turning up the heat on the serious business of late-night comedy ratings. Nearly a year after NBC chieftain Jeff Zucker proclaimed Leno was so far ahead in the ratings that "there is no more late-night war," CBS boasted Thursday that Letterman was on the comeback trail, narrowing the gap against a fading Leno.