Will viewers line up to see a five-hour miniseries about the Jackson clan? If so, ABC could break a historic drought when it comes to major sweeps periods.At the midway point of the fall Nielsen ratings survey, ABC heads into the current weekend in first place, giving the alphabet network an opportunity to claim its first November sweeps win in 14 years. Through Wednesday night, ABC is averaging a 12.9 rating, 21 share, holding a narrow lead over CBS (12.6/20) and NBC (12.0/19). On Sunday, ABC will kick off its five-hour mini “The Jacksons: An American Dream,” which closes next Wednesday. The network is hoping the multiparter can rival the performance of CBS’ recent “Sinatra”–which crooned a tuneful 17.5/27 over two nights– with a better young-demographic skew. ABC hasn’t won a November sweeps since 1978 and, in fact, has won only five of the last 29 major sweeps periods (held annually in November, February and May) going back to February 1980. Two of those victories, in February 1980 and ‘ 88, came on the strength of the quadrennial Winter Olympics. The other wins were in February ’83 and May ’82 and ’84. Fox leaps and bounds Year to year, Fox Broadcasting Co. has posted the most significant gains, averaging an 8.5/13 halfway through the four-week survey, up 9% in rating over last year despite expanding to a new night. ABC and CBS are close to last year’s performances–down 1% and up 2%, respectively–while NBC, the eventual winner last November, is off 9% compared to ’91. Fox is also the only prime time service to improve in terms of adults 18-49, the key sales demographic, up 8% from last year. The ratings sweeps are significant because stations, especially those in smaller un-metered markets, use the survey periods to determine local advertising rates. A strong network performance can help boost affiliate newscasts, particularly those following prime time. Sweeps cycles The history of sweeps has been cyclical, with the top-rated network of the day holding sway for long stretches. ABC, for example, won 11 consecutive sweeps, from February 1976 through May ‘ 79, when Aaron Spelling’s hours were dominating the airwaves. More recently, NBC took 18 out of 20 major sweeps, between May 1985 and November last year, before handing over the seasonal ratings crown to CBS.