NBC wrapped the first week of May sweeps with a dominant performance Wednesday, as all three of its programs won their hours in key demos and lifted the net to its most lopsided Wednesday victory among young adults in more than nine years.

According to Nielsen, the Peacock picked up steam throughout the night, with “Ed,” “The West Wing” and “Law & Order” gaining viewers and demo ratings with each half-hour.

Net’s 40% advantage over second-place ABC in adults 18-49 (6.0/17 vs. 4.3/12) is its largest on a Wednesday since January 1992, while its 5.3 million viewer advantage over second-place CBS is its largest in overall audience on the night since May 1991.

Off to good start

Wednesday’s action capped the opening week of the four-week May sweep. Night also saw continued ratings erosion for Fox’s “Boot Camp” and nice turnouts for CBS’ “Murder, She Wrote” movie and ABC’s season finale of “Once and Again.”

For NBC, “Ed” kicked things off by winning its hour with a 4.1/13 in adults 18-49 (more than doubling the hour’s score of a year ago, 1.9/6). “West Wing” dominated its hour in total viewers (16.61m) and adults 18-49 (6.3/16, up 43% vs. a year ago), as did “Law & Order” (19.67m, 7.6/20 in A18-49), which topped the combined demo scores for ABC and CBS.

ABC finished second in 18-49 (4.3/12), with rookie family laffer “My Wife and Kids” winning its half-hour at 8 (4.1/14) and the wedding episode of “Once and Again” delivering that drama’s best numbers (9.34m, 4.6/12 in 18-49) since March 7, and best-ever opposite an original “Law & Order.”

At 8:30, “Two Guys and a Girl,” back on Wednesdays, held a so-so 90% of “Wife’s” demo lead-in (3.7/12).

Fox placed third in 18-49 (4.2/13) and delivered year-to-year gains for the fifth consecutive night, although “Boot Camp” (9.32m, 4.7/12 in A18-49) fell to new lows. The reality series still prevailed in adults 18-34 (5.5/16), helping the net win the night by that measure over NBC (4.9/15 vs. 4.6/14).

Viewers, ‘She Wrote’

CBS sacrificed demos for viewers Wednesday, as new “Murder, She Wrote” pic “The Last Free Man” (11.32m) helped the net to a rare total-viewer victory in the 8 p.m. hour but settled for a fourth-place finish in adults 25-54 (2.7/7). Pic drew the largest aud for a single-part Eye Wednesday movie since January.

But at 10, “48 Hours” logged the smallest aud for any edition of the newsmag (7.71m) since January.

It was very close among the web-

lets on Wednesday, with the WB and UPN both averaging a 1.9/5 in adults 18-49 and the Frog leaping barely ahead in total viewers (3.86m vs. 3.85m); both were up vs. the same night a year ago.

It was no contest among younger viewers, though, as the WB’s combo of “Dawson’s Creek” and “Felicity” topped UPN’s “Special Unit 2” and “Star Trek: Voyager” in adults 18-34 (2.6/8 vs. 1.3/4) and teens (2.9/10 vs. 1.2/4).

Through seven nights of the sweep, NBC leads in adults 18-49 with a 5.0/14 (down 2% in rating vs. a year ago), followed by Fox, 4.3/13 (up 8%); ABC, 3.8/11 (down 38%); CBS, 3.6/11 (up 9%); UPN, 1.5/4 (down 6%), tied with the WB, 1.5/4 (even).

In total viewers, CBS leads the way with 12.4 million (up 4%), followed by NBC, 12.1m (up 4%); ABC, 10.7m (down 36%); Fox, 8.9m (up 8%); UPN, 3.6m (down 9%); and the WB, 3.4m (down 2%).