New York ? If “The West Wing” were the real White House, glum-faced presidential operatives would be obsessing over worrisome poll numbers.

The Emmy-winning political drama’s decline in popularity is the most puzzling and dramatic example among a handful of established NBC programs that have suffered sluggish starts this television season.

“The West Wing” ratings are down 23 percent compared to the first three episodes last year, according to Nielsen Media Research. “ER” is down 15 percent. After a fast start with Niles and Daphne’s wedding, “Frasier” has sunk. “Providence” is off 19 percent.

“A network always needs to be concerned about the health of their returning series, simply because they are the pillars of their schedule,” said Stacey Lynn Koerner, a television analyst for Initiative Media. “It’s a lot easier to replace a new show that is not living up to expectations.”

ABC is still trying to recover from a ratings free fall after established hits like “The Drew Carey Show” and “Who Wants to Be a Millionaire” swiftly lost favor last fall.

No one suggests such a dire forecast for NBC, since it’s a solid No. 2 to CBS so far this season and No. 1 in the 18-to-49-year-old age demographic it is most concerned about.

But the numbers have been noticed.

“Everyone is trying to write the ‘NBC cracks’ story, but we’re in a different universe. We’re happy,” said NBC Entertainment President Jeff Zucker on Wednesday. “There’s no question that ‘The West Wing’ is off to a slow start and ‘Frasier’ is down. Beyond that, we’re thrilled.”

NBC is particularly pleased with its performance on Sunday nights with the new “American Dreams” and on Monday nights with “Fear Factor,” he said. And Zucker noted that “ER,” which was seen by 24.7 million viewers last week, has been able to stay among TV’s top shows despite cast defections, including Anthony Edwards at the end of last season.

“‘ER’ is probably our biggest success story of the season,” he said.

Theories about “The West Wing” abound: viewer exhaustion with politics, critics who say its quality has slipped. NBC is facing tougher competition in the time slot, particularly for young viewers, with ABC’s “The Bachelor” and the WB’s “Birds of Prey.”

Even though “The West Wing” hit Nielsen’s top 10 last week, “The Bachelor” won among viewers age 18 to 49.

“Given the tremendous competition for young adults in that hour, this is probably a realistic place for the show to be,” Zucker said.

Ironically, the show’s slow start may end up helping NBC financially: NBC and the show’s producer, Warner Bros. Television, need to reach a new agreement to extend the show beyond this season.

Some of the other NBC shows are showing their age. “Frasier” is in its 10th season, and “ER” is in its ninth. “Providence,” which was on the fence for renewal before this season, began in January 1999.

The age-defying “Law & Order” franchise is becoming a bigger part of NBC’s success, said analyst Marc Berman of Media Week Online.

Still, NBC has been less successful in establishing the constant flow of new blood needed by a network to regenerate itself, he said.

“It’s the beginning of a bad period,” Berman said, “because these shows aren’t going to do any better for them.”

Second-year comedy “Scrubs,” which follows “Friends” on Thursdays, is averaging 7 percent fewer viewers than last year’s “Inside Schwartz,” which was canceled after four weeks.

NBC research guru Mitch Metcalf said that the network got an encouraging sign when last week’s “Scrubs” held on to a season-high 70 percent of the top-rated “Friends” audience.

If it can build on that percentage, “we’ll be very happy with its performance in a difficult time period,” Metcalf said.

Other experts cautioned against drawing too many conclusions on the basis of three weeks of ratings, especially when comparing them to last year’s unusual, post-Sept. 11 viewing habits.

“I think you have to wait a few weeks to see what’s really happening,” said Steve Sternberg, an analyst for Magna Global USA.

CBS last week widened its lead over NBC in total viewers for the second week in a row. CBS averaged 13.2 million viewers compared with NBC’s 12.4 million, according to Nielsen Media Research.