NEW YORK — Just before a new NBC News president gets to work, her division is seeing another longtime winning streak come to an end.
For the first time since November 2008 — a stretch of 243 straight weeks — ABC's "World News" beat NBC's "Nightly News" last week in viewership among the 25-to-54-year-old demographic that forms the basis for many advertising sales, the Nielsen company said.
While not as epochal as "Good Morning America" dethroning the "Today" show last year, Tuesday's ratings report is a sign of concern for Brian Williams' nightly newscast. NBC News will see a new leader shortly, when Deborah Turness arrives from Britain's ITV News, and she's facing challenges to the division's long-time leadership role.
When all viewers are counted, particularly older people who are traditionally the heaviest viewers of television news, NBC won last week. But so far this season among all viewers, ABC is closer to NBC than it has been in five years.
Michael Corn, executive producer of "World News," said he and anchor Diane Sawyer are proud of ABC's behind-the-scenes team, the local ABC stations and viewers.
"We have a lot more work to do," Corn said. "We're just getting started."
ABC's strong week came even though Sawyer was replaced by David Muir for three days out of five. The birth of England's royal baby and Robin Roberts' exclusive interview with a juror in the Zimmerman murder trial were strong sellers for ABC.
NBC notes that its audience tends to dwindle during the summer months, compared to its rivals, and that overall NBC had its strongest competitive July against ABC in four years.
Among all viewers, "Nightly News" averaged 7.5 million people, "World News" had 7.3 million and the "CBS Evening News" had 6 million, the Nielsen company said.
"We are grateful for another consecutive win in total viewers and are focused on producing the best newscast for our audience," said Erika Masonhall, NBC News spokesperson.
The CBS miniseries "Under the Dome" was the week's most popular prime-time show last week, with 11.6 million viewers.
CBS won the week in prime time, averaging 5.6 million viewers. NBC had 4.5 million, Univision had 3.83 million, ABC had 3.76 million, Fox had 3.2 million, Telemundo had 1.7 million, ION Television had 1.3 million and the CW had 900,000.
The Disney Channel was the week's most popular cable network, averaging 2.7 million viewers in prime time. USA had 2.4 million, TNT had 2.1 million, History had 1.9 million and Fox News Channel had 1.7 million.
For the week of July 22-28, the top 10 shows, their networks and viewerships were: "Under the Dome," CBS, 11.6 million; "America's Got Talent" (Wednesday, 9 p.m.), NBC, 10.64 million; "America's Got Talent" (Tuesday), NBC, 10.34 million; "60 Minutes," CBS, 8.36 million; "The Big Bang Theory," CBS, 8.07 million; "NCIS," CBS, 7.18 million; "Unforgettable," CBS, 7.15 million; "Big Brother 15" (Thursday), CBS, 6.9 million; "Big Brother 15 (Sunday), CBS, 6.81 million; "Two and a Half Men," CBS, 6.79 million.