I remember when Chet Huntley retired, NBC tried a rotating-anchor system of David Brinkley, John Chancellor, and Frank McGee, The gimmick was that only two would appear on any given night and you had to tune in to see which two. Viewers didn't go for it; they wanted to see the same person every night. Chancellor became the anchor of NBC Nightly News, McGee went to the Today Show to replace Hugh Downs, and Brinkley did commentaries (although he and Chancellor re-teamed for NBC's 1976 election coverage and co-anchored Nightly News for about three years). I don't know how relevant this is some 50 years on, because the nightly network news is not the draw it was in the '70s, but it is a precedent. The era of Brokaw, Jennings, and Rather was the last golden era of network news.