The Clinton campaign is upping its attacks on Bernie Sanders, now characterizing his performances as “unstable.”

Brian Fallon appeared on CNN on Thursday and when asked about whether he thought Sanders would have “specific answers” to questions, the press secretary instead seemed to question the mental fitness of his candidate’s opponent.

“I assume you know he’s going to be asked a lot of specific questions,” Wolf Blitzer told Fallon.

“Well, we’ve seen in all the debates up until now, uh, unstable performances from Sen. Sanders especially when it comes to details on foreign policy, how he’s going to combat ISIS,” Fallon said.