CBS has muscled its way to first in May 5-11 primetime Nielsens and into a tie for the May sweeps households lead, thanks largely to “The Last Don,” which started its run with CBS’ highest Sunday-pic rating in two years.In the adults 18-49 demo, though, older-skewing CBS remains at the bottom of the Nielsen river. It’s NBC that continues to dominate the 18-49 race (a key measure in determining ad revenue) for both the May sweeps and the May 5-11 week, despite hefty losses vs. year-ago numbers. All challengers are being thwarted by mixed results from sweeps-month stunts. For every “Last Don” or “Ellen” success, there’s a “Knots Landing” or “20,000 Leagues Under the Sea” disappointment to keep NBC’s challengers at bay. Through Monday of this week, 19 days into the four-week sweeps, household averages are: CBS, a 10.1 rating, 17 share (up 2% in rating vs. results for the same period last year), tied with NBC, 10.1/17 (down 18%); ABC, 9.0/15 (even); Fox, 7.2/12 (even). There’s no race to speak of in adults 18-49, where 19-night averages are: NBC, a 6.7 rating (down 17%); ABC, 5.7 (up 14%); Fox, 5.2 (up 6%); CBS, 4.3 (down 2%). CBS is currently third in its target demo of 25-54, edging out Fox. If CBS’ “Last Don” can maintain its momentum through Tuesday and Wednesday episodes this week, CBS is likely to build a modest sweeps-month advantage over NBC in households. That would put some pressure on the Peacock’s late-month stunts (“The Odyssey,” a 3-D “3rd Rock From the Sun” and a baby’s birth on “Mad About You”) to make up that difference by the May 21 wrap-up of the sweeps. Last week’s adults 18-49 averages were: NBC, 6.7/19 (down 14%); Fox, 5.1/15 (down 6%), tied with ABC, 5.1/14 (even); CBS, 4.3/12 (down 4%); UPN, 1.8/5 (up 13%); WB, 1.2/3 (up 20%). NBC says it’s poised to become the first net in 10 years to win back-to-back seasons by more than a full point in adults 18-49. Monday On Monday of this week (May 12), Fox stole the night by 3 shares among adults 18-49 with the latest of its controversial reality specs, “Video Justice: Crime Caught on Tape” (8.9 rating, 14 share in homes). ABC’s “20,000 Leagues Under the Sea” sunk to a two-night 7.6/12, apparently the second-lowest rating ever for an in-season firstrun multiple-parter on the Big Three, beating only ABC’s disastrous “Apocalypse Watch” (5.1/8) from earlier this season. The third-highest-rated “Chicago Hope” of the season (12.3/21) led CBS to victory in homes and adults 25-54. “Ink” (11.2/17), with guest star Candice Bergen as “Murphy Brown,” contribbed a best-yet 97% retention of its lead-in from “Cybill” (11.6/18). Sunday “The Last Don” roughed up the competition with CBS’ highest Sunday-pic rating since “Buffalo Girls, Part 1,” April 30, 1995, and the second-best first-episode rating among the 13 multiple-parters launched by the nets this season. However, CBS’ nightlong win demonstrates why the Eye has a decent shot at winning the sweeps in homes but will probably finish last in adults 18-49. CBS led this night by an overwhelming 11 shares in households but actually finished 2 shares behind Fox (7-10 p.m.) in 18-49 results. Fox has won that 7-10 p.m. block in adults 18-49 on eight of the last nine Sundays, with “The X-Files” leading its hour each week during the sweeps despite hyper-competitive opposition. Bulls-Hawks hoops dominated the 7-8 p.m. hour among adults 18-49 for NBC, despite falling 26% below year-ago Bulls-Knicks results. ABC’s “Angels in the Outfield” foretold possible misfortune for a regular Sunday Disney film, landing deep in the timeslot cellar in adults 18-49. Saturday While CBS dominated in homes, NBC pulled away in adults 18-49 and 25-54. It was NBC’s widest Saturday 18-49 margin of victory with series programming in the five years since May 2, 1992 (the night of the second-to-last “Golden Girls”). In its planned fall slot, “The Pretender” beat CBS’ tiring “Dr. Quinn” by 7 shares in adults 18-49. In homes, “Dr. Quinn” hit its lowest firstrun rating ever and lowest for CBS in that slot since Nov. 14, 1992. Friday ABC won the night, based mostly on the strength of “20/20″ and its interview of O.J. prosecutor Marcia Clark. Also, a special “America’s Funniest Home Videos” gave the “T.G.I.F.” lineup a bit of a boost at 9:30. Fox faded to third behind NBC in adults 18-49 with its lowest firstrun Friday average since the summer of ’95. A CBS challenge failed to materialize as “Knots Landing: Back to the Cul-de-Sac” stayed deep in last among adults 18-49. “Knots” ‘ disappointing two-night households average (9.1/16) puts it behind 10 of the season’s 12 completed multiple-parters. Thursday NBC climbed to the highest nightlong 18-49 rating of the sweeps, though “Fired Up” stumbled on its path toward renewal. Last week, “Fired” flickered to NBC’s worst 18-49 lead-in retention in that post- “Seinfeld” slot (72%) since Jan. 26, 1995. “Living Single’s” season petered out with that sitcom’s second-lowest firstrun homes rating ever. “Living” was still second that hour in adults 18-49. Wednesday “Ellen” managed barely half its previous-week record rating, but still impressed, building by 14% on its 18-49 lead-in from “Drew Carey.” That’s a big turnaround in a slot where ABC has averaged a 14% falloff. The 3-D episode of “Carey” enjoyed that series’ highest rating in eight weeks. Fox owned the 8-9 p.m. hour as “Beverly Hills 90210″ led in adults, men and women in the 18-34, 18-49 and 25-54 breakouts. CBS passed NBC for the night in adults 18-49 with part one of “Knots,” CBS’ highest-rated Wednesday pic of the season. At 8:30, though, the just-benched “Dave’s World” is hurting its dimming renewal chances, last week losing 16% of its 18-49 lead-in from “The Nanny.” Tuesday ABC maintained its grip on Tuesday, as 3-D episodes of “Home Improvement” and “Spin City” popped out to those series’ best results in five weeks. At 8:30, a special “Grace Under Fire” showed it’s still a solid schedule mate to “Improvement,” building by 17% on its 18-49 lead-in from a repeat of that Tim Allen sitcom. NBC’s Tuesday numbers unexpectedly contracted, with “Mad About You” feeling its most painful firstrun rating in more than four years (since Saturday, March 6, 1993) and “Frasier” equaling its lowest firstrun rating ever. Monday The firstrun finale of “Married … With Children” led Fox to a solid 18-49 win on Monday (5) with its best Monday average since November (Daily Variety, May 7). NBC led in homes and adults 25-54 with “Invasion,” the fourth-highest-rated multiple-parter out of 12 on the nets this season among adults 18-49. Each rating point represents an estimated 970,000 households, or 1% of the country’s TV homes. The share is the same sort of percentage, except that it’s measured against only the households in which TV is being watched during the timeslot involved.