(taken from imdb:)
In a new blow to NBC, which will soon be losing its hit show Friends and has seen ratings plummet for another onetime hit, Frasier, West Wing creator Aaron Sorkin, who is also its primary writer, announced Thursday that he will leave the series this month. "I had the best job in show business for four years and I'll never forget that," Sorkin said in a statement. Joining him will be the show's executive producer and lead director Thomas Schlamme. John Wells, whose company co-produces the show with Warner Bros., said that he expects to assume a more active role with it next year. Ratings for the West Wing have declined precipitously this season, particularly among 18-49-year-olds, the demographic group courted most zealously by advertisers.