When you're the undisputed champion, people are always watching for the first hint of vulnerability. The undisputed champion is News Corp.'s (NYSE:NWS) Fox network show, American Idol, and recent Nielsen stats suggest its stranglehold on the American viewership might be loosening.

Last week, an ABC show, Grey's Anatomy, actually managed to sneak into second place for the week, behind AI Wednesday but ahead of AI Tuesday. In the role of up and coming contender for the crown, you might also look at Dancing With The Stars on the Walt Disney Co. (NYSE: DIS) network, which handily won Monday night this week. The finale, won by Apolo Ohno and Julianne Hough, drew a 10.2 rating and a 17 share.

Looking beyond the slight decline in American Idol viewership, however, I see a still-thriving franchise. Part of the decline can be attributed to shrinking television viewership, part to time-shifting via DVD recorders, and part to those who prefer to watch on-line.

American Idol continues to clobber its competitors in the market sector that really matters to advertisers, those 18-49 years of age.

On a more parochial level, stories about AI are among the most read on this blog. I can only conclude we must have a huge News Corp. stockholder following!