Thanks largely to the strength of the network’s prime-time dominance, CBS’s “Late Show” closed the gap some on NBC in the November sweeps.

Although “The Tonight Show with Jay Leno,” which has dominated the late-night ratings for much of the past decade, still holds a sizable lead over David Letterman’s “Late Show,” Letterman managed to shrink Leno’s lead during sweeps to less than a million viewers. “The Late Show” drew 5.08 million viewers per night in sweeps, compared to 5.86 million for “The Tonight Show.”

In November 2003, by comparison, “The Tonight Show” held a lead nearly twice as big, drawing 6.2 million viewers to “The Late Show’s” 4.6 million. Letterman’s show has also made the race among adults 18-49, averaging a 1.8 rating in the ad-friendly demographic for sweeps versus Leno’s 2.1. In November 2003, Letterman drew a 1.7 and Leno a 2.4.

The improved numbers for “The Late Show” are due primarily to the fact that CBS now holds a commanding lead in primetime. It beat second-place NBC by more than 3.5 million viewers in sweeps and also finished first among adults 18-49 – the first time that’s happened in a November sweep since 1980.

CBS has three 10 p.m. EST shows – “CSI: Miami” on Mondays, “CSI: NY” on Wednesdays and “Without a Trace” on Thursdays – that are leading their timeslots this season, giving strong lead-ins to local newscasts and “The Late Show.” NBC is competitive on Wednesday and Thursday (and sometimes wins among adults 18-49) with “Law & Order” and “ER,” so “The Tonight Show” continues to win those nights.

On Mondays, however, “CSI: Miami” dominates its competition, which has allowed “The Late Show” to beat or tie its rival among adults 18-49 on seven of the eight Mondays when both were airing new episodes this season.