When a new show debuts to huge numbers, the question always is whether that momentum will carry or whether it will slump in the following episodes.

It seems a clear case of the former for Fox’s new hit game show “Are You Smarter Than a 5th Grader?” For the third straight night, the Jeff Foxworthy-hosted quiz show put up huge numbers, managing to hold most of its “American Idol” lead-in.

“Smarter” averaged a 9.4 adults 18-49 rating last night, according to Nielsen overnights, retaining 90 percent of lead-in “Idol’s” 10.4.

“Smarter” was down a tad from Wednesday’s 9.7, but its lead-in dipped as well. On a night where the other networks aired mostly reruns, Fox earned its third straight nightly win in dominant fashion, more than doubling CBS.

Not surprisingly, Fox has ordered four additional episodes of “Smarter” and scheduled them for Thursdays at 8 p.m. That’s in addition to already announced episodes airing the next three Thursdays.

“Smarter’s” numbers will likely dip once “Idol” contracts back from Thursday to a two-night schedule two weeks from now, but it should give Fox a Thursday presence that it has lacked for years. Even if the show lost half its audience, it would still compete for No. 1 in the timeslot.

Fox was first for the night among 18-49s with a 9.9 average rating and a 24 share. CBS was second at 4.2/11, ABC third at 2.9/7, NBC fourth at 2.8/7, Univision fifth at 1.9/5 and CW sixth at 1.0/2.
 
At 8 p.m. Fox started the night in the lead with a 10.4 rating for its “Idol” results show. CBS was second with a 5.0 for “Survivor,” NBC third with a 3.0 for repeats of “My Name is Earl” and “The Office” and Univision fourth with a 2.3 for “La Fea Mas Bella.” ABC was fifth that hour with a 2.2 for a repeat of “Ugly Betty” and CW sixth with a 1.1 for a “Smallville” rerun.
 
Fox led again at 9 p.m., this time with a 9.4 for an hour of “Smarter.” CBS came in second with a 4.3 for a repeat of “CSI,” ABC third with a 3.9 for a repeat of “Grey’s Anatomy” and NBC fourth with a 3.0 average for “Scrubs” (3.4) and “30 Rock” (2.7). Univision slipped to fifth that hour with a 1.9 for “Mundo de Fieras” and CW was sixth with a 0.9 for a repeat of “Supernatural.”
 
CBS led a rerun-filled 10 p.m. hour, finishing on top with a 3.2 for a repeat of “Shark.” ABC was second with a 2.6 for a repeat of “Men in Trees,” NBC third with a 2.4 for a repeat of “Black Donnellys” and Univision fourth with a 1.5 for “Aqui y Ahora.”
 
Fox led the night easily among households, finishing with a 14.2 average rating and a 21 share. CBS was second at 9.0/14, ABC third at 5.6/9, NBC fourth at 4.0/6, Univision fifth at 2.2/4 and CW sixth at 1.6/2.