CBS rookie drama ”Person of Interest” has been picking up steam in its rookie season, tying ABC’s ”Grey’s Anatomy” for Thursday’s demo lead in the 9 o’clock hour and helping the net take the night. Fox’s ”American Idol,” meanwhile, fell further but was still the night’s No. 2 show.

Fox won only one half-hour but earned a tie for the night with CBS in adults 18-49 while the Eye won easily in adults 25-54 and total viewers.

According to preliminary national estimates from Nielsen, ”Person of Interest” averaged a 3.1 rating/8 share in adults 18-49 and 14.4 million viewers overall, rising 10% from last week when it faced atypical competition from ”American Idol.” ”Person” tied ABC’s ”Grey’s Anatomy” for the middle hour’s lead among young adults , its most competitive finish to date (even if ”Grey’s” edges up to beat ”Person” in the nationals). ”Person” also held a 10% advantage over the ABC drama in adults 25-54 (4.2/10 to 3.8/9).

CBS remained strong kicking off the night with ”The Big Bang Theory” (5.2/15 in 18-49, 16.1 million viewers overall), which was up a bit week to week and opened up its biggest advantage yet over ”American Idol” (5.2 to 4.0 in 18-49, 6.6 to 5.3 in adults 25-54 and 16.1 million to 14.0 million in total viewers). It was followed by ”Rob” (3.0/8 in 18-49, 10.6 million viewers overall), which posted its lowest score to date but still earned a solid second-place finish to Fox’s ”Idol.”

The night’s 10 o’clock hour was won across the board, at least on the broadcast side, by CBS’ ”The Mentalist” (2.5/7 in 18-49, 13.2 million viewers overall), which was down a bit week to week. It topped ABC’s ”Private Practice” (2.2/6 in 18-49, 6.4 million viewers overall), which was also down, and NBC’s special off-night repeat of ”Grimm” (0.9/3 in 18-49, 2.2 million viewers overall).

At Fox, ”American Idol” (4.4/13 in 18-49, 15.4 million viewers overall) was down more than 10% week to week for a season low; in its second half-hour, its 4.9 demo score beat the combined deliveries of the next two closest broadcasters (CBS and NBC). Following ”Idol,” first-year drama ”The Finder” had another soft showing (2.0/5 in 18-49, 6.2 million viewers overall).

NBC was on par with its week-earlier scores in the night’s opening hour with ”30 Rock” (1.5/4 in 18-49, 3.7 million viewers overall) and ”Parks and Recreation” (1.7/5 in 18-49, 3.4 million viewers overall). And from 9 to 10, ”The Office” (2.6/7 in 18-49, 5.0 million viewers overall) and ”Up All Night” (1.8/4 in 18-49, 3.5 million viewers overall) bounced back from their lows of last week opposite ”American Idol” and also were up a tick vs. two weeks ago when they faced the same competition as last night.

ABC opened modestly with ”Wipeout” (1.5/4 in 18-49, 5.0 million viewers overall) and then picked up at 9 with ”Grey’s Anatomy” (3.1/8 in 18-49, 8.9 million viewers overall), which was on the low end but still tied with ”Person of Interest” as Thursday’s No. 1 drama in 18-49.

CW aired repeats of ”The Vampire Diaries” (0.5/1 in 18-49, 1.3 million viewers overall) and ”Supernatural” (0.3/1 in 18-49, 0.9 million viewers overall).

In addition to MTV’s tough ”Jersey Shore” at 10, Thursday’s cable competition earlier in the evening included a buzzed-about NBA basketball game on TNT between the Miami Heat and New York Knicks, which was watched in 3.4% of U.S. households, according to preliminary Nielsen data from TNT. The game (roughly 7-9:30 p.m. ET) was a big draw in the local markets, scoring a 9.4 household rating in Miami and a 15.3 in Miami-Ft. Lauderdale.

Preliminary 18-49 averages for the night: CBS and Fox, 3.2/9; ABC, 2.3/6; NBC, 1.6/4; Univision, 1.3/4; CW, 0.4/1.

In total viewers: CBS, 13.7 million; Fox, 10.8 million; ABC, 6.8 million; Univision, 3.5 million; NBC, 3.3 million; CW, 1.1 million.