Second-half dynamo Fox has captured the primetime demo derby for a fifth consecutive week, setting up what should be a down-to-the-wire finish for the season title.

Massive ratings for a two-hour “American Idol” on Tuesday ensured Fox’s rather easy victory among adults 18-49, with its 5.0 rating/13 share well ahead of CBS (3.8/19), ABC (3.6/10) and NBC (3.2/10), according to in-home viewing estimates by Nielsen.

Net also led in adults 25-54 (5.4/13) and persons 12-34 (4.2/13) while placing a close second to CBS in total viewers (11.9 million to 12.0 million).

At roughly the three-quarters mark of the season, Fox (4.0) has pulled to within one-tenth of a rating point of 18-49 leader ABC (4.1), with CBS at 3.9. The Alphabet and Fox appear headed for a tie at 4.1, although a lot can happen with more than eight weeks to be counted.

The top three nets are as snug as can be in nonsports averages — a better indication of each net’s strength in entertainment programming: ABC, CBS and Fox are all at a 3.8 rating, with NBC at a 3.2. A strong finish should help Fox win in this category.

CBS is looking good to win in adults 25-54 for a third straight season, and there’s nothing stopping the net from its fourth straight crown in total viewers.

Among program rankings at the three-quarters mark, Fox’s “American Idol” editions on Tuesday and Wednesday tower over the pack, followed in 18-49 by ABC’s “Desperate Housewives” and “Grey’s Anatomy” and CBS’ “CSI.”

“CSI” looks to finish as the most-watched scripted series for a fourth straight season.

Among comedies, CBS’ “Two and a Half Men” and NBC’s rookie “My Name Is Earl” are deadlocked for the 18-49 lead, with “Men” expected to win the season in 25-54 and total viewers.

“Earl” should finish as the top new scripted series on any net in 18-49, and the Eye’s “The Unit” is poised to rank No. 1 in 25-54 and total viewers.

Looking at the week of March 20-26, “American Idol” on Tuesday was easily the top-rated program in all key categories including adults 18-49 (13.6 rating/33 share) and total viewers (33.36 million).

Wednesday’s “Idol” results show ranked second in 18-49 (11.4/27), and the program that followed it, the debut of “Unanimous,” ranked fourth (7.1/20) — the best retention for a post-“Idol” bow in two years.

Fox also rocked Monday with “24” (5.5/13 in 18-49, 13.71m) and the spring premiere of “Prison Break” (4.3/11, 10.27m). And Sunday’s live-action intro on “The Simpsons” lifted that vet laffer to its best scores since the fall (5.0/13, 10.09m).

At CBS, “The Unit” (4.2/9, 15.50m) again looked good, and new comedy “Old Christine” (5.1/12, 15.13m) built on its week-earlier premiere. (“Christine” didn’t look as good on Monday of the current week (3.8/9, 11.96m), as the hit shows sandwiching it were in repeats.)

The Eye also was competitive Thursday and won Friday with third-round action of the NCAA men’s basketball tourney. Sunday’s late game between Florida and Villanova bled into overtime, helping lift “60 Minutes,” which featured a two-part segment on Tiger Woods, to its best scores in a couple of months (4.3/11 in 18-49, 17.09m).

ABC was paced by original episodes of “Desperate Housewives” (8.9/20 in 18-49, 21.41m) and “Lost” (6.6/15, 16.06m) as well as a repeat “Grey’s Anatomy” (6.6/16, 14.85m) — the best score for an Alphabet rebroadcast in six years.

“American Inventor” (5.1/13, 13.04m) again looked good on Thursday, leading into the highest-rated edition of “Primetime” (4.5/12, 10.86m) in 2½ years. Not looking very special was Wednesday’s premiere of “The Evidence” (3.4/9, 9.10m), which fumbled much of its “Lost” lead-in.

NBC showed rare year-to-year growth thanks to three nights of “Deal or No Deal.” Gamer set series records on Monday (5.6/14, 16.80m) and then delivered the net’s best regular-series scores Wednesday at 8 in more than five years (5.1/14, 14.95m).

On Wednesday, the premiere of “Heist” failed to excite auds (3.0/8, 8.75m), although it did build on its soft lead-in from “Law & Order” in its new time period (2.6/6, 9.00m).

The week in cable was highlighted by Comedy Central’s Sunday spec “Ron White: You Can’t Fix Stupid” (2.0/4 in 18-49, 4.49m), which drew the third-largest aud in net history. Also boosted by “South Park” and “Mind of Mencia” earlier in the week, Comedy Central moved up to third for the frame among cablers in 18-49, and ranked No. 1 in men 18-34.

Another strong performer was Disney Channel’s Friday series premiere of “Hannah Montana,” which averaged 5.44 million viewers and did a 31 share in female teens.

Tough Tuesday competish on the broadcast nets clobbered a pair of premieres on Bravo: The return of “Blow Out” drew just 521,000 viewers at 9 p.m., while the debut of “The Real Housewives of Orange County” notched just 430,000 at 10.