Hitting nearly 21 million viewers, CBS drama vet ”NCIS” powered the net to a demo victory on Tuesday, while ABC’s comedy newcomer ”Work It” had a sluggish showing in its second week on the job.

According to preliminary national estimates from Nielsen, ”NCIS” dominated the night’s opening hour , and was also easily Tuesday’s No. 1 program overall , with a 4.1 rating/11 share in adults 18-49 and 20.9 million total viewers. The net then remained on top at 9 p.m. with ”NCIS: Los Angeles” (3.5/8 in 18-49, 17.1 million viewers overall), and 10 p.m. rookie drama ”Unforgettable” (2.2/6 in 18-49, 11.2 million viewers overall) tumbled in demos week to week but remained the broadcast leader for its hour.

CBS won the night by 2 shares in adults 18-49 and by 5 shares in adults 25-54. In total viewers, it beat the combined tune-in of ABC, NBC and Fox.

NBC placed second on the night among young adults, as ”The Biggest Loser” held steady week to week (2.4/6 in 18-49, 6.7 million viewers overall) and ”Parenthood” (1.8/5 in 18-49, 4.8 million viewers overall) edged up from its series low of last week to place second among the broadcasters for the 10 p.m. hour in adults 18-49.

At ABC, ”Last Man Standing” matched its lowest score to date leading off the night (2.2/6 in 18-49, 7.9 million viewers overall), and ”Work It” followed with a soft 1.6/5 in 18-49 and 5.1 million viewers overall , down 20% from last week’s 2.0 in the demo. Despite the lighter lead-in, ”Celebrity Wife Swap” (2.1/5 in 18-49, 5.2 million viewers overall) matched its score from last week and 10 p.m. drama ”Body of Proof” (1.6/4 in 18-49, 6.9 million viewers overall) was up a tick from its series low of the previous week.

Fox, which returns to originals next week, aired encores of Tuesday regulars ”Glee” (1.1/3 in 18-49, 3.1 million viewers overall), ”New Girl” (1.3/3 in 18-49, 3.3 million viewers overall) and ”Raising Hope” (1.0/3 in 18-49, 2.8 million viewers overall).

Preliminary 18-49 averages for the night: CBS, 3.2/8; NBC, 2.2/6; ABC, 1.9/5; Univision, 1.4/4; Fox, 1.1/3; CW, 0.3/1.

In total viewers: CBS, 16.3 million; ABC, 6.2 million; NBC, 6.0 million; Univision, 3.3 million; Fox, 3.1 million; CW, 0.7 million.