Fox’s “American Idol” continued its decline Wednesday, hitting a low and finishing behind the combo of “CSI” and “Survivor” on CBS in key demos. Those two nets were in a virtual draw as the top networks on a night that also saw a promising start for CW drama “The 100.”

According to preliminary national estimates from Nielsen, “The 100” averaged a 0.9 rating/3 share in adults 18-49 and 2.7 million viewers overall in the 9 o’clock hour, building on its lead-in from “Arrow” (0.8/3 in 18-49, 2.4 million viewers overall). The post-apocalyptic drama based on a book of the same name fared especially well in New York, where its 1.5 rating/4 share in adults 18-49 edged out “American Idol” (1.4/4).

This was the largest audience in the Wednesday-at-9 hour for CW since September 2010, and it’s the net’s most popular midseason premiere since “Life Unexpected” in January 2010. Compared to the last original episode of “The Tomorrow People” in the hour, “The 100” delivered at least double the rating in just about every demo category as well as total viewers.

At CBS on Wednesday, “Survivor” (2.4/8 in 18-49, 9.6 million viewers overall) was on par with last week’s 18-49 delivery and won its hour in key demos and total viewers over Fox’s “American Idol” (2.2 in the demo and 9.5 million in the hour). This is the second straight week that “Survivor” has pulled ahead of the Fox show head-to-head in demos, and Wednesday’s victory in total viewers — if it holds in the nationals — would be the CBS show’s first ever over “Idol.”

“Criminal Minds” followed at 9 (2.2/7 in 18-49, 10.1 million viewers overall), down slightly from last week and finishing a tick behind “American Idol” in 18-49 and 25-54 while winning in total viewers for the third time in its last four original telecasts. And closing things out, “CSI” (2.0/6 in 18-49, 10.1 million viewers overall) matched last week’s demo score and matched the combined 18-49 deliveries of timeslot rivals “Chicago PD” and “Nashville” (in repeat).

As for “American Idol,” its two-hour averages (2.2/7 in 18-49, 9.7 million viewers overall) repped week-over-week declines of a little over 5% in both the demo and total viewers for the show’s lowest performance-episode scores to date. For the night, Fox tied with CBS in adults 18-49 while pulling narrowly ahead in 18-34 and 25-54.

At NBC, “Revolution” (1.2/4 in 18-49, 4.3 million viewers overall) was down a tick to what would be its series low. It was followed by “Law & Order: SVU” (1.5/4 in 18-49, 5.6 million viewers overall) and the recently renewed “Chicago PD” (1.4/4 in 18-49, 6.0 million viewers overall), which were also down from last week.

ABC aired mostly repeats, opening with “The Middle” (1.3/4 in 18-49, 5.1 million viewers overall), “Suburgatory” (1.1/3 in 18-49, 4.1 million viewers overall) and “Modern Family” (1.7/5 in 18-49, 5.4 million viewers overall). An original “Mixology” aired at 9:30 p.m. (1.2/3 in 18-49, 3.6 million viewers overall), down 20% (0.3) to a low, and the evening ended with an encore “Nashville” (0.6/2 in 18-49, 2.4 million viewers overall).

Preliminary 18-49 averages for the night: CBS and Fox, 2.2/7; NBC, 1.4/4; ABC, 1.1/3; Univision, 1.0/3; CW, 0.8/3; Telemundo, 0.5/1.

In total viewers: CBS, 9.9 million; Fox, 9.7 million; NBC, 5.2 million; ABC, 3.8 million; CW, 2.5 million; Univision, 2.1 million; Telemundo, 1.2 million.