NEW YORK (AP) — CBS' Sunday morning public affairs television show "Face the Nation" has clearly gotten under the skin of its rivals at NBC's "Meet the Press."

NBC accuses CBS of some trickery in the Nielsen ratings and in scheduling designed to make its show seem more popular than it actually is. CBS detects the aroma of sour grapes. The incident is a vivid illustration of a newly competitive era on Sundays.

As recently as last year, David Gregory's "Meet the Press" was the clear leader among these programs, averaging 3.21 million viewers per week, according to Nielsen, a company that measures media consumption. "Face the Nation" had 2.68 million viewers and ABC's "This Week" was at 2.32 million, with "Fox News Sunday" in fourth.

Things are much tighter so far this year. "Meet the Press" has dropped to an average of 2.91 million, CBS has climbed to 2.82 million and "This Week" has 2.39 million, Nielsen said.

To NBC, those numbers present an incomplete picture.

Until April, "Face the Nation" broadcast for a half hour each week. ("Meet the Press" and "This Week" are hour-long shows.) With its fortunes improving, Bob Schieffer's CBS show expanded to an hour this spring. Yet at CBS' request, Nielsen still reports ratings for the first half hour to advertisers and the media.

Reporting on the full hour would depress the numbers for "Face the Nation." On Sept. 9, for example, the CBS show had 2.49 million viewers in its first half hour, and 1.12 million in its second half hour, Nielsen said.

If "Meet the Press" is judged on a full hour's worth of ratings, so should "Face the Nation," said Erika Masonhall, NBC News spokeswoman.

"We are constantly now forced to fight back against a false narrative about the state of the Sunday morning public affairs programs," she said. That narrative: NBC is struggling on Sunday compared with surging CBS.

CBS argues that only two-thirds of the country is now showing the full hour of "Face the Nation." Some stations break the program up, showing the second half hour later in the day. With football and basketball season, more western cities will be temporarily cutting back to a half hour in the coming months. CBS hopes that by next spring, more than 90 percent of the country will show the full hour.

Networks often play sleight of hand games with Nielsen numbers designed to make themselves look better. For example, morning news shows have been known to replace all of their national commercials in the last half hour or so with local ads. Thus, Nielsen won't include that time — which generally has the smallest audience — in its national ratings.

CBS points out that NBC's "Today" show is regularly judged on its ratings for the 7 to 9 a.m. portion of its show, even though it is now on for four hours a day.

"This is a very, very close and competitive business right now," Schieffer said. "My advice to the competition would be to try to put on the best broadcast you can. I think you'll find that time would be best spent, rather than in engaging in other activities."

Masonhall also accused CBS of deceptively touting an interview with President Barack Obama on "Face the Nation" last week, when instead the show played a small portion of an interview that Scott Pelley conducted with the president for the "CBS Evening News." Gregory interviewed Republican presidential candidate Mitt Romney on his show last week.

Again, a television news show offering portions of material that had been gathered for another show on the network is hardly unusual. NBC does it, too.

"We have never misled people," Schieffer said.

NBC News may be feeling the pressure of two of its signature news programs losing their dominant status. After an impregnable 17-year run on top of the ratings, "Today" has suddenly slipped behind ABC's "Good Morning America." ''Meet the Press" had an unchallenged run at the top before the death of host Tim Russert in 2008. Brian Williams of "Nightly News" is the network's last unquestioned leader in its time slot.

Sunday morning dominance is worth more than bragging rights. Advertisers pay more to be on the top show, and newsmakers want to go where they can be seen by the most people.

With the return of George Stephanopoulos, ABC has also become more competitive. In fact, the ABC show beat both of its rivals on Sept. 2, with its largest lead over CBS in two years. Viewers switch around to shows that have the best guests, making for a volatile ratings race, Schieffer said.

"So much of it depends on who you have," he said. "It used to not be. In the days of Tim Russert, Tim could bring along a test pattern and show it and he would win the week. But those days are long gone, and people have to adjust to it."

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