There’s no doubt that “American Idol,” after years of monster ratings, is slowing down. Last night the reality juggernaut tied a season low, also one of its lowest outings in years. The problem for the other networks is that even a diminished “Idol” remains way out ahead of the competition.

“Idol” averaged an 8.8 adults 18-49 rating, according to Nielsen overnights, tying a season low set last week and the lowest Tuesday mark since 2003. The show did rise slightly week to week in total viewers, from 23.6 million to 24 million.

But even with “Idol” down, the other networks couldn’t take advantage. The other Big Four combined for a 6.3 rating in the 8 p.m. timeslot, 40 percent behind “Idol.”

“Idol’s” certainly not the only show seeing its ratings slip lately. ABC’s “Desperate Housewives,” CBS’s “Survivor” and NBC’s “ER” have all hit series lows in recent weeks, while other shows returning from the writers’ strike have seen ratings declines compared with last year.

In its seventh season, “Idol” remains the No. 1 show on television in the demographic, well ahead of ABC’s “Housewives” and Fox’s own “House.”

Fox was first for the night among viewers 18-49 with a 6.9 average overnight rating and an 18 share. ABC was second at 2.7/7, NBC third at 2.3/6, CBS fourth at 2.1/6, Univision fifth at 1.7/4 and CW sixth at 0.9/2.
 
At 8 p.m. Fox was first with an 8.8 rating for “Idol,” followed by CBS with a 2.9 for “NCIS.” Univision was third with a 1.9 for “Al Diablo con los Guapos,” ABC fourth with a 1.4 for an hour of “According to Jim,” NBC fifth with a 1.3 for “Most Outrageous Moments” and the first half hour of a “Saturday Night Live” special, and CW sixth with a 0.7 for “Beauty and the Geek.”
 
Fox was first again at 9 p.m. with a 5.1 for “Hell’s Kitchen,” with ABC second with a 4.0 for “Dancing with the Stars.” CBS was second with a 2.4 for “Big Brother,” Univision fourth with a 1.9 for “Pasion,” NBC fifth with a 1.7 for another hour of the “SNL” special and CW sixth with a 1.0 for “Reaper.”
 
NBC took the lead at 10 p.m. with a 4.0 for “Law & Order: Special Victims Unit,” while ABC took second with a 2.8 for “Boston Legal.” Univision was third with a 1.3 for “Aqui y Ahora” and CBS fourth with a 1.1 for “Shark.”
 
Among households, Fox was first for the night with a 10.4 average overnight rating and a 16 share, followed by ABC at 7.0/11, CBS at 5.6/9, NBC at 4.4/7, Univision at 2.1/3 and CW at 1.3/2.