ABC’s Sunday and Fox’s Tuesday may be the hotter lineups, but CBS’ Thursday sked flexed its muscles last week, kicking off the May sweep with a dominant ratings victory.

“Survivor,” “CSI” and “Without a Trace” — together on the night for a fourth season — overwhelmed the competish in key demos to start the four-week ratings period that puts a cap on the 2005-06 season. CBS was also impressive Friday with its potent drama trio of “Ghost Whisperer,” “Close to Home” and “Numbers.”

According to national estimates from Nielsen for Thursday, CBS was off slightly in adults 18-49 from the first full Thursday of May 2005 but actually opened up a wider margin of victory over NBC (6.7 to 4.0) because the Peacock tumbled 26% year to year.

It was an impressive showing for the Eye, especially since leadoff hitter “Survivor” (5.9/18 in 18-49, 17.09 million viewers overall) was down 17% vs. last year’s first full Thursday in May — although up vs. recent weeks. The reality vet more than doubled the 18-49 numbers of NBC combo “Will & Grace” (2.8/9, 7.58m) and a repeat “My Name Is Earl” (2.8/8, 6.87m).

Star of the night remains “CSI” (8.7/22 in 18-49, 27.37m), which was off only slightly year to year and beat ABC, NBC and Fox combined in adults 25-54 (11.1/26 to 9.8/23).

Its competish wilted, with NBC’s “My Name Is Earl” (4.1/11, 9.05m) and “The Office” (3.9/10, 7.85m) down 31% from “The Apprentice” of a year ago, while Fox’s “The OC” (2.4/6, 5.41m) was off sharply from last year, when it aired two segs.

At 10, “Without a Trace” (5.5/15, 17.93m) was up slightly year to year, while NBC’s “ER” (5.2/14, 12.34m) dropped 27% to fall behind its CBS rival in all categories except 18-34.

ABC was flat vs. a year ago, drawing an OK perf from “American Inventor” at 9 (3.0/8 in 18-49, 7.30m) but struggling at 10 with “Commander in Chief” (1.8/5, 6.51m).

Friday saw more declining numbers for “The Daytime Emmy Awards” (prelim 1.8/6 in 18-49, 6.3 million), with this year’s three-hour telecast on ABC sliding more than 15% from last year’s two-hour show on CBS to place third for the night.

The Eye took the night thanks to a solid second-place perf at 8 from “Ghost Whisperer” (prelim 2.9/10 in 18-49, 9.7 million) and winning scores from “Close to Home” (prelim 3.0/9, 11.1m) and “Numbers” (prelim 3.4/11, 12.2m).

NBC again started strong with “Deal or No Deal” (3.2/12, 11.1 million) before falling off with “Las Vegas” (2.6/8, 8.2m) and “Conviction” (2.0/6, 6.2m), according to Nielsen prelims.

Fox did nothing Friday with “Austin Powers in Goldmember” (prelim 1.3/5 in 18-49, 3.3 million) but won Saturday as usual in key demos, powered by “America’s Most Wanted” (prelim 2.7/9 in 18-49, 6.9m).