NBC Nightly News with Brian Williams posted its lowest ratings in at least 20 years last week.

The broadcast dipped below seven million viewers, averaging 6,840,000 viewers -- its smallest audience since the advent of people meters, and probably well before then.

Williams anchored two nights last week; Lester Holt filled in Wednesday through Friday.

The same week last year, also a holiday week, NBC averaged 7,220,000 viewers...