America's three original network news shows face the same momentous choice at nearly the same time: Pass the torch to a new anchor who, each hopes, has the gravitas to hold viewers and win new ones, or break with a star-driven tradition developed back in television's Pleistocene era and try something different. This moment of transition - brought on by the departures of Dan Rather at CBS and Tom Brokaw at NBC, and now Peter Jennings's decision to curtail appearances on ABC's news broadcasts - brings into stark relief some of the ongoing challenges for the networks. Even with established...