All four judges – L.A. Reid, Demi Lovato, Simon Cowell and Britney Spears – were impressed by Sonenclar's rendition of the Adele chart-topper "Rolling in the Deep."
"I thought the first half of the song was good," Cowell said to the 13-year-old. "I thought the second half of the song was sensational."
A former child star herself, Lovato said she had no critique for Sonenclar this week. "Carly, I'm not even your mentor and I feel proud of you."
Sonenclar secured the No. 1 spot with audience votes last Wednesday after her performance of "Somewhere Over the Rainbow" got a standing ovation from the judges. She told "X Factor" that she was shocked by the news at first.
"Being in the No .1 spot, I did not expect it at all,” she said. “I was just extremely happy."
"At this point, anybody can win this," she said. "It's very important not to get too comfortable in the No. 1 spot. Every week the competition gets more and more intense. So I have to give everything I have so that I can stay in the top spot."
Sonenclar’s competition mentor, Spears, wanted to raise the bar for performances. "Let everybody else sing the oldies and we’ll bring it," Spears said. "It’s right at your fingertips now."
"X Factor" judge Reid said that even though "Rolling in the Deep" wasn’t his favorite performance by Sonenclar, her "second best is better than everybody else's first best."
Cowell ran with a joke from last week, saying that Sonenclar may be not be able to take the top prize.
"The only problem we have, which we've established, is you're not human," Cowell said. "So therefore, you may have to be disqualified from this competition because aliens aren't allowed to enter."
"Darn it," Sonenclar replied with a laugh.
Lovato was impressed that Sonenclar was still just a normal 13-year-old when she stepped on stage, even after singing such soulful songs. "I just think you're so cute and you're so young and there's something really genuine about that."
"X Factor" returns Thursday night at 8 with the results from viewer votes, which Sonenclar hopes still have her No. 1.