ELLEN DEGENERES leaves no opportunity untapped, not even a few seconds of chat on “American Idol.”

Casey James, this season’s golden-haired heartthrob, was waiting for Ms. DeGeneres, the newest judge on “American Idol,” to assess his performance of the Rolling Stones hit “It’s All Over Now.” Ms. DeGeneres began with his good looks  and her own public persona.

“Casey, for most women, their hearts are going to start racing just looking at you, right, but then, for people like me ...” She paused, holding the beat while judges and audience members tittered over the implied allusion to her being a lesbian. As the laughter swelled, Ms. DeGeneres held up a finger, prolonging the joke. Then, with a knowing grin, she delivered the punch line: “...blondes ...”

Ms. DeGeneres, one of America’s most popular female comedians and talk-show hosts, is also one of its most beloved gay entertainers  and one of the few who markets herself as such. And she finds a way to remind audiences of her sexual status on almost every episode of “American Idol.” More than in any other of her ventures, Ms. DeGeneres’s performance on America’s favorite television show suggests how hard she works to seem effortlessly funny and how determined she is to be openly but unthreateningly gay. She doesn’t need the work, but she appears to want the demographic  “Idol” is her chance to expand her reach to a younger, more pop-obsessed audience, the Hulu Generation of viewers, who prefer to download their entertainment rather than press the remote. And Ms. DeGeneres, funny, irreverent and also quite cautious onstage, is setting herself up as the Jon Stewart figure on “Idol” that people under 30 can trust.

She already has their parents. Her syndicated talk show, “The Ellen DeGeneres Show,” was an instant hit when it went on the air in 2003, reviving a career that had faltered after she came out as a lesbian in 1997. She is now a leading candidate for Oprah Winfrey’s throne when “The Oprah Winfrey Show” closes down next year. And that’s just her daytime realm. She has punched every ticket to mainstream success: she was a fish in the Disney-Pixar animated film “Finding Nemo,” she has hosted the Emmys and the Oscars, and currently she stars in ads for American Express, Vitaminwater Zero and Simply Ageless cosmetics for Olay and CoverGirl  a coup for a lesbian in her 50s best known for a tomboyish, no-makeup look.