NEW YORK (AP) — Oprah Winfrey is opening her talk show’s 24th season with a flourish. One week of programs include a Chicago block party with the Black Eyed Peas, an exclusive Whitney Houston interview, her first Dr. Phil visit in seven years and a trip to New York.

It’s hard to remember when it seemed more important.

Winfrey is still the queen of daytime television, but the aura of invincibility is gone. The average viewership for “The Oprah Winfrey Show” slipped under 7 million last season, down 7 percent from the year before, according to Nielsen Media Research. One week during the July rerun season, the show had its lowest ratings since its 1985 debut.

There are many possible explanations for the fade, including some over which Winfrey has no control. Ratings declines are common with so many choices and demands on time, particularly during the day. It’s even rarer for programs that have been on the air as long as Winfrey’s to grow.

And it’s not just her. “Live with Regis and Kelly” had the same 7 percent decline last season. Shows with Jerry Springer, Maury Povich and Martha Stewart all had double-digit declines.

Yet Winfrey has also alienated some of her audience, particularly in more conservative parts of the country, said Janice Peck, author of the book “Age of Oprah” and a University of Colorado professor.

By endorsing Barack Obama and campaigning for him, she shucked her apolitical image. Winfrey’s book club selection of Eckhart Tolle’s New Age religion book “A New Earth” angered some conservative Christians — even though Winfrey’s producer said Winfrey was careful not to push Tolle’s views on viewers through the television show.

Winfrey’s buoyant encouragement of her audience, telling them that their possibilities are limitless, may no longer resonate in tough economic times, Peck said.

The professor said few of her college students talk about Winfrey. They seem more interested in Ellen DeGeneres or Tyra Banks. As the just-named fourth judge for “American Idol,” DeGeneres is in line for a burst of attention this year.

“They see Oprah as kind of like who their mom likes,” she said. “This is not a good sign for her.”

Sheri Salata, executive producer, acknowledges “The Oprah Winfrey Show” is trying to deal with the delicate issue of attracting young viewers while not alienating longtime fans. Notice how the block party carefully followed a performance by the Black Eyed Peas with one by James Taylor.

It was the first time the show actively used social networks, drawing a crowd of 21,000 people in part through alerts on Twitter and Facebook, she said.

Winfrey has aggressively promoted her interview with Houston, telling Mario Lopez during an appearance on “Extra” that it was the best one she has ever done.

Whoa. Mario Lopez? Interviews with Winfrey used to be harder than that to come by.

“You can’t be oblivious to the decline in ratings,” said Bill Carroll, expert in the syndication market for Katz Television. “Even if it is the dominant show, you have to look at what the value is. I am sure that the people around her are aware of the trends or the perception of trends.”

Salata said the show is trying hard to make an impact with the season opening, although it does that every year.

“When you’ve been on the air for 24 years, our greatest challenge as producers is what are we going to do now that hasn’t been done before? How do we take it up a notch?” she said.

Big interview “gets” like Houston or Erin Andrews, the sportscaster who was secretly videotaped nude, are important. The show will also do a “Mad Men” inspired episode where everyone, from the audience to Winfrey, is dressed in early 1960s style, she said.

“We have a real commitment to our viewers to do shows that will make their lives better, and that’s not something we take lightly,” she said.

It’s worth remembering that Winfrey still has the most-watched talk show by a wide margin, more than two million viewers over “Dr. Phil.” But downticks in its ratings have an impact beyond her: most stations use her show to give a big audience lead-in to their local news. NBC used to argue that ABC’s “World News” got a ratings boost because Winfrey’s show was on many ABC stations, even though it was two hours before the network news.

How things go this fall will affect an important decision: Winfrey is signed to do her show through September 2011, and has promised an answer by the end of the year on whether she’ll renew her contract.

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