An expanded 90-minute episode of “American Idol” produced an easy primetime ratings victory for Fox on Tuesday night, while it was a mediocre bow for the return of “Amazing Race” on CBS.

From 9 to 10:30, “American Idol” dominated as usual with a 12.3 rating/30 share in adults 18-49 and 29.7 million viewers overall; show continues to be performing 12% above of last year’s 18-49 average at this point of the season. At 9:30, first-year comedy “The War at Home” (6.0/14 in 18-49, 13.5 million viewers overall) notched its best score ever with a special post-“Idol” episode designed to give it more sampling.

CBS ran second from 8 to 9, but was on the low end of its range, with “NCIS” (3.4/9 in 18-49, 14.9 million viewers overall). And from 9 to 11, the ninth edition of “The Amazing Race” was also a bit sluggish (4.0/10 in 18-49, 10.3 million viewers overall) — down 18% from the premiere of “Race 7,” which bowed during the same week a year ago.

NBC got more good mileage out of gamer “Deal or No Deal” (3.3/8 in 18-49, 10.0 million viewers overall), delivering the net’s best series showing in the hour opposite “Idol” in two years. “Scrubs” was on the high end at 9:30 with the second of its two original episodes (3.6/9 in 18-49, 8.3 million viewers overall), but “Law & Order: SVU” was below par at 10 despite winning the hour (4.9/12 in 18-49, 13.7 million viewers overall).

Fourth-place ABC was led by “Boston Legal” at 10 (3.4/9 in 18-49, 11.2 million viewers overall).

Preliminary 18-49 averages for the night: Fox, 10.7/26; CBS, 3.8/10; NBC, 3.8/9; ABC, 2.8/7; WB, 2.0/5; UPN, 0.6/1.

In total viewers: Fox, 25.7 million; CBS, 11.8 million; NBC, 10.4 million; ABC, 8.4 million; WB, 4.5 million; UPN, 1.3 million.