• by David Goetzl  @dgoetzl, November 4, 2010

As election returns rolled in Tuesday, CBS scored a victory of sorts as it toppled NBC and ABC in total viewers and households for 30 minutes. Perhaps helped by "NCIS: Los Angeles" leading in, CBS drew 6.7 million viewers in the 10 p.m-10:30 p.m. period -- 8% above second-place NBC -- and had a winning 4.5 household rating.

However, the two metrics dropped precipitously for CBS in the next half-hour as it dropped to third, where it remains during the nightly newscasts. The three networks went head-to-head in election coverage in prime time only in the 10 p.m. hour.

From 10 p.m. to 10:30 p.m., CBS' average of 6.7 million viewers was above NBC's 6.2 million and ABC's 5.7 million. Households had CBS' 4.5 above NBC's 4.1 and ABC's 3.8. (NBC still beat CBS in the 18-to-49 demo.)

But in the back half of the hour, ABC led CBS by 7% in viewers, and NBC led both significantly with 6.3 million. Households had CBS at 3.4, trailing NBC's 4.2 and ABC's 3.6.

CBS had strong ratings at the top of the hour with "NCIS: Los Angeles" that kick-started its lead. NBC and ABC had lower-performing election coverage as lead-ins.

At least for programming with heavy live viewing such as news, a lead-in still carries weight. ABC trounced NBC in election coverage in the 9:30 p.m. to 10 p.m. period following "Dancing with the Stars."