Colbert won in the Nielsen company's ratings for the ninth consecutive time last week, his margin of 400,000 viewers the widest lead since the CBS star overtook Fallon with a sharp concentration on politics. Boosted by the NCAA tournament, CBS dominated last week with an average of 9.7 million viewers in prime time. NBC had 5.3 million, ABC had 4.4 million and Fox had 2.7 million.