Fox dominated Wednesday’s primetime ratings race behind ”American Idol” and ample sampling for the preview episode of drama ”Touch,” while CBS carried the night’s final hour as the ”CSI” swansong for original cast member Marg Helgenberger produced season highs for the show.

According to preliminary national estimates from Nielsen, ”American Idol” averaged a 6.4 rating/18 share in adults 18-49 and 19.5 million viewers overall to rate well above any other show on the night in both categories. The music talent competition was off about 7% from last week’s opening hour (and about 12% from its two-hour premiere average) — roughly the same falloff it saw from week one to two a year ago. It was followed by the debut of Kiefer Sutherland drama ”Touch” (3.9/10 in 18-49, 11.9 million viewers overall), which led its hour in 18-49, 25-54 (4.9/11) and all key male demos; Fox notes that no drama debuting after ”American Idol” in recent years (including ”Glee,” ”Fringe” and ”Lie to Me”) has held onto more of the megahit’s young-adult audience than ”Touch.”

”Touch” isn’t scheduled to return to the Fox lineup until March 19, when it will follow ”House” on Mondays in a return for Sutherland to his old ”24” timeslot.

CBS opened with a repeat of ”Criminal Minds” (1.7/5 in 18-49, 7.9 million viewers overall), followed by the 150th original episode of the show at 9 (3.6/9 in 18-49, 13.7 million viewers overall), which was up 13% week to week. And at 10, ”CSI” hit season highs (3.3/9 in 18-49, 14.0 million viewers overall) as Helgenberger’s character of Catherine Willows said goodbye to the ”CSI” team after more than 11 years together.

ABC aired repeats of its regular lineup: ”The Middle” (1.5/4 in 18-49, 5.3 million viewers overall), ”Suburgatory” (1.4/4 in 18-49, 4.2 million viewers overall), ”Modern Family” (2.5/6 in 18-49, 6.5 million viewers overall), ”Happy Endings” (1.7/4 in 18-49, 4.0 million viewers overall) and ”Revenge” (0.9/2 in 18-49, 3.1 million viewers overall).

At NBC, the leadoff comedy combo of ”Whitney” (1.4/4 in 18-49, 4.5 million viewers overall) and ”Are You There, Chelsea” (1.4/4 in 18-49, 3.9 million viewers overall) came down a bit more in their third outings, in line with the repeat ABC comedies in the hour. They were followed by encores of ”Law and Order: SVU” (1.2/3 in 18-49, 3.8 million viewers overall) at 9 and then at 10 p.m. in its regular timeslot (1.4/4 in 18-49, 4.0 million viewers overall).

And CW’s original ”One Tree Hill” (0.7/2 in 18-49, 1.5 million viewers overall) and repeat ”Remodeled” (0.3/1 in 18-49, 0.7 million viewers overall) were on par with last week.

Preliminary 18-49 averages for the night: Fox, 5.2/14; CBS, 2.9/8; Univision, 1.7/4; ABC, 1.5/4; NBC, 1.3/4; CW, 0.5/1.

In total viewers: Fox, 15.7 million; CBS, 11.9 million; ABC, 4.4 million; NBC, 4.0 million; Univision, 3.5 million; CW, 1.1 million.