BEIJING, Feb. 8 -- Ellen DeGeneres makes her much-anticipated debut on "American Idol" on Tuesday, shaking up the dynamics on the show's judging panel and auditioning her own talents for the biggest TV audience in the United States.

The arrival of the popular talk show host and comic is expected to boost viewership on the Fox television network's aging singing contest, now in its 9th season and facing challenges to its coveted spot as the No. 1 show on U.S. TV.

DeGeneres, 52, takes the seat held by Paula Abdul, who quit last summer in a contract renewal dispute, and "Idol" fans and TV critics remain passionately divided over her replacement.

Comedian Ellen Degeneres poses with her award for Favorite Talk Show Host at the 35th annual People's Choice awards in Los Angeles January 7, 2009.

She lacks the music industry credentials of fellow judges, Randy Jackson, a record producer; songwriter Kara DioGuardi; and sharp-tongued Simon Cowell, who has his own record label and two other TV talent shows.

But the witty talk show host said she aimed to be the voice of the viewer at home.

"I'm someone who knows what it's like to be on stage and entertain. So I know what it takes. It's not like I don't listen to music constantly," she said in a TV interview last week.