Ratings Chart Attack!

With TV use down due to St. Patrick’s Day celebrations, Tuesday night’s reality heavyweights “American Idol” and “Dancing With the Stars” sank to near-record lows.

Due to the holiday, TV use was down compared with last Tuesday, particularly among young adults (36.2% vs. 37.6%), having a significant effect on shows across the board.

“Idol,” as expected, was the top show of the night and gave Fox the Tuesday win. Last night’s two-hour episode, featuring performances from the top 11 finalists, finished the night with an 8.0 rating/22 share among adults 18-49 and 21.5 million viewers, according to preliminary Nielsen figures. However, “Idol” was down 16% from last week’s episode and off 24% from last year, coming in as the lowest-rated Tuesday episode since August 2002, during season one.

In its first head-to-head telecast against “Idol” this season, “Dancing With the Stars’” first results show at 9 p.m. scored a 2.7/7 (12.4 million), down 27% from its comparable episode last September and down 31% from last spring’s first results show. Tuesday’s show is the franchise’s lowest premiere episode and the series’ lowest-rated regular episode. ABC opened the night with a “Dancing” recap (1.7/5, 8.1 million) and finished with a new “Primetime: What Would You Do?” (2.3/7, 7.8 million). The network finished fourth with an average 2.2/6 (9.4 million).

NBC’s “The Biggest Loser” scored a 3.2/9 (7.9 million), taking a 16% dip from last week. This edition of “Loser,” however, has showed a 14% gain for the season-to-date compared with the same weeks last year and is drawing the franchise’s biggest audience, averaging 10.4 million viewers in its 10 weeks. At 10 p.m., “Law & Order: SVU” (3.4/10, 10.6 million) was down 6% from last week but ranked as the No. 1 show in its time period. Overall, NBC finished second for the night with a 3.3/9 (8.8 million).

CBS’ dramas returned last night with season lows. A new “NCIS” kicked off the night with a 3.1/9 (15.5 million). At 9 p.m. a fresh “The Mentalist” scored a 3.2/8 (15.4 million), down 14% from its last original episode. “Without a Trace” was down only a tick from its last original, rounding off the night with a 2.5/7 (12 million). CBS placed third for the night with a 2.9/8 (14.3 million).

The CW’s “Reaper” (0.8/2, 1.9 million) was down one-tenth of a rating point. Along with an encore “90210,” the network averaged a 0.6/2 (1.3 million) in the demo, and a 0.6/2 among women 18-34.