In a ratings result that should only strengthen the resolve of writers to settle the strike, Fox opened its lie-detector reality series “Moment of Truth” to huge ratings Wednesday night behind “American Idol.”

Bowing after “Idol,” of course, is a guaranteed way to get auds to sample a show, but most seemed to like what they saw. It retained more of its 18-49 lead-in from the music show than any show to date, and actually built on “Idol” in younger viewers.

Among the 18-34 crowd, it’s the best start to any series in five years.

For the night, opposite a mix of reality and scripted fare from 8 to 10 p.m., the Fox reality offerings crushed the combined rating of the competish by about 25% among adults 18-49.

“It went far beyond my expectations,” Fox alternative topper Mike Darnell enthused. But the exec said he had a hunch that “Moment of Truth” would skew young. “Empirically, the people who were most excited about the show were college kids and younger people.”

The show worked, he said, because it’s “an incredibly relatable concept.”

“If you want to win the money, you’ve got to tell the truth,” Darnell said. “That leads to great drama. It’s possibly breaking families apart, possibly ruining relationships or at the very least getting the truth out into the open.”

Darnell said he thought the show was particularly compatible with “Idol” at the moment because the competish is still in its early phase.

“It’s the ‘humiliation section’ of ‘Idol,’ ” he noted — and “Moment of Truth” is all about humiliation.

According to Nielsen national estimate that include same-night DVR playback, “American Idol” kicked off the night for Fox with another dominant performance (10.9 rating/28 share in adults 18-49, 27.09 million viewers overall), even if it did come in 13% below its delivery in the same hour a year ago. It beat its combined ABC-CBS-NBC competition by 11 shares in 18-49.

And at 9, “Moment of Truth” (10.2/24 in 18-49, 23.05m) retained a record 94% of its 18-49 lead-in from “Idol,” logging the best numbers for a premiering show on any network since last February’s “Are You Smarter Than a 5th Grader,” which also bowed behind “Idol” on Fox.

“Moment” skewed younger than “5th Grader,” though, actually building on “Idol” by 7% in adults 18-34 and posting the best premiere score on any net in this demo (10.5/27) since Fox’s “Joe Millionaire” in January 2003.

“Moment of Truth” declined in its second half-hour (from a 10.9/26 in the demo to a 9.5/23) but was still the overwhelming ratings winner at 9:30, beating ABC, CBS, NBC and CW combined.

The show, from Lighthearted Entertainment and hosted by Mark Walberg, will air for three more weeks behind “Idol” before eventually sliding into its regular 8 o’clock timeslot on the night in March.

Fox has 12 episodes of “Moment of Truth” in the bank, but Darnell said he wouldn’t be surprised if the net ordered additional segs in the next few days. Like most gameshows, “Moment” can jumpstart production almost immediately.

Elsewhere Wednesday, NBC ran second thanks to a solid yet distant runner-up finish to “American Idol” for “Deal or No Deal” at 8 o’clock (3.7/9 in 18-49, 13.66m).

In an hour of all reality shows on the broadcast networks, “Deal” crushed ABC’s “Wife Swap” (1.9/5, 5.57m), CBS’ “Power of 10” (0.8/2, 3.63m) and CW’s “Crowned” (0.7/2, 1.37m). “Deal” numbers repped the best showing in the time period for NBC in 13 months, and it’s the best series perf in this hour opposite “Idol” for the net since 2004.

CBS put up the best numbers at 9 opposite Fox’s “Moment of Truth” with an original episode of “Criminal Minds” (3.2/8 in 18-49, 12.67m) and then won at 10 p.m. with “CSI: NY” (3.2/8 in 18-49, 11.51m). “CSI: NY” topped its firstrun drama competish from NBC’s “Law & Order” (3.0/8, 10.35m) and ABC’s “Cashmere Mafia” (2.0/5, 5.58m).

ABC’s best numbers on the night came at 9 o’clock from a third-place finish for “Supernanny” (2.8/7 in 18-49, 7.18m).

And final national cable ratings for Tuesday showed a record-setting finale for Bravo’s “Real Housewives of Orange County” (1.1/3 in 18-49, 2.02m) — up about 25% over the season-two finale. “Housewives,” along with “Project Runway” and the new “Make Me a Supermodel,” have the cabler poised to finish with its best-ever numbers for the month of January.

(Michael Schneider contributed to this report.)