Viewership for Fox’s “American Idol” may be down this season, but don’t count out primetime’s reigning champ just yet.

Last week, Wednesday’s performance show marked its third straight sesh atop the weekly young-adult series program rankings, holding off NBC’s own music competition skein, “The Voice.”

The shows don’t compete head-to-head, but they have been in close battles for bragging rights honors in the with Monday series “The Voice,” riding momentum from its debut after the Super Bowl, finishing higher than “Idol” in four of their first five common weeks. Over the last three weeks, though, “Idol” has prevailed.

Last week saw the Wednesday “Idol” (5.3 rating/15 share in adults 18-49, 17.87 million viewers overall) rule as TV’s No. 1 series in 18-49 while “The Voice,” which now faces formidable femme competish from ABC’s “Dancing With the Stars,” settled for the silver (4.5/12 in 18-49, 12.00m).

For the season, “The Voice” is clearly NBC’s top-rated entertainment series and up vs. last year (though recent trend lines have diminished those gains) while “Idol” is down by more than 20% — its first significant year-over-year falloff after holding up surprisingly well in the years since its peak season of 2006.

These days, “Idol” is consistently the top draw among the two music contests in adults 25-54 and total viewers while “Voice” is setting the pace among adults 18-34.

Despite its recent run atop the charts, “Idol” may still have a tough time making it an eighth straight season as primetime’s No. 1 entertainment series in adults 18-49. That’s because “The Voice” was able to include its hugely rated season premiere following the Super Bowl (a whopping 16.3 rating in the demo) into its averages; a seldomly applied Nielsen rule allows the premiere rating for a Monday series that opens its season on a Sunday (within 24 hours of its regular Monday timeslot) to count in season averages.

In the most current Nielsen numbers through Sunday that include full-week DVR playback through March 18, “Voice” was averaging a 7.0 rating in 18-49 to a 6.6 for “Idol.”

Overall for the week of March 26-April 2, CBS used a pair of college basketball tourney games and the “Academy of Country Music Awards” to cruise in adults 18-49 — its third straight week on top (including one tie). The Eye’s 2.8 rating/8 share in the demo was followed by Fox (2.2/7), ABC (1.8/5), NBC (1.6/4) and Univision (1.2/3).

CBS also finished on top in adults 25-54 (3.7/10) and total viewers (11.5 million) for a fourth straight week.

In adults 18-34, Univision finished third (1.6/5) for a seventh straight week.

The Eye claimed the week’s top show in 18-49 with the Final Four college basketball contest between Kansas and Ohio State (5.5/17, 16.60m), up a bit vs. last year’s comparable game, while the “ACMs” (3.1/8, 13.09m) were down a bit year to year but lifted the net to a Sunday victory.

On the entertainment series side, “NCIS” (3.5/11, 18.62m) was the week’s No. 1 drama in 18-49, 25-54 and total viewers, while its “The Big Bang Theory” was the top comedy and scripted program overall in demos (4.7/15, 13.96m). Also, the net’s Thursday rookie “Person of Interest” returned strong after a two-week break (3.3/9, 14.59m).Elsewhere for Fox, Thursday drama “Touch” (2.7/7, 8.92m) fell off from its week-earlier preem but retained a solid 61% of its “Idol” results show lead-in (4.4/13, 15.87m) and placed second at 9. Not so hot was another first-year drama, “Alcatraz,” which wrapped with quiet numbers (1.5/4, 4.75m).

ABC was led by “Dancing With the Stars” (3.2/8, 17.96m) and Sunday hours “Once Upon a Time” (2.8/8, 8.39m) and “Desperate Housewives” (2.6/6, 8.49m). Also looking good were Monday’s “Castle” (2.3/6, 11.87m) and Friday’s “20/20” (2.1/7, 7.01m), with the latter scoring with a lottery-themed edition.

In its third week, Thursday drama “Missing” (1.5/5, 7.87m) edged down another tick.

NBC, in fourth place for a third straight week, was led by “The Voice,” its Monday leadout “Smash” (2.1/5, 6.14m) and “Celebrity Apprentice” (1.8/5, 5.96m).

Leading the way among adults 18-49 in cable were HBO’s season preem of “Game of Thrones” (2.0/5, 3.86m) and USA vet “WWE Raw” (1.7/5, 4.45m). In other categories, History’s “Swamp People” was on top among basic cablers in adults 25-54 (1.9/5), a tick behind “Thrones” (2.0/5); MTV’s debut of “Pauly D Project” was No. 1 in adults 18-34 (2.2/8); and Nick’s “Kids’ Choice Awards” led in total viewers (6.16m).

And among the nets, TBS led in all key 18-54 age groups while USA prevailed easily in total viewers.

Also of note, Fox News Channel’s “O’Reilly Factor” was Wednesday’s most-watched primetime news telecast (3.48 million) — besting NBC’s struggling “Rock Center” (3.02m).