Demi Lovato Sings Mariah Carey Classic 'All I Want For Christmas Is You' (Video)

The "X Factor" judge boldly attempts the holiday staple while the First Family looks on.

As Randy "Broken Record" Jackson might warn aspiring pop star wannabes on American Idol, you should never, ever, ever even begin to think about singing a Mariah Carey song in public because her voice encompasses something like eight octaves and few can measure up to her diva greatness.

Apparently Demi Lovato doesn't heed that sort of advice: The X Factor judge boldly stepped into the spotlight to pay homage to her new American Idol competition on TNT's Christmas in Washington special, broadcast Friday. In the front row: President Obama and the First Family.

Our verdict? Demi is no Mimi, but she managed a decent version of the song (on par with the finale of Love, Actually, you know the scene). Some people suspect Carey's not taking this very well.