A spokesman for Hillary Clinton, Brian Fallon, on Wednesday criticized Sen. Bernie Sanders (I-VT) as the only “holdout” who will not participate in an unsanctioned debate to be hosted by MSNBC and the New Hampshire Union-Leader in February.

“The Sanders campaign is the one hold out. We think they should join us in saying they will be in New Hampshire next week,” Fallon said on CNN.

Sanders’ campaign manager, Jeff Weaver, said on Tuesday that the Vermont senator would not attend a debate not sanctioned by the DNC due to concern that his participation would keep him from attending future official debates.

Clinton’s campaign said she would “participate in a debate in New Hampshire if the other candidates agree, which would allow the DNC to sanction the debate.” And former Maryland Gov. Martin O’Malley said he would attend the unsanctioned debate.

The DNC said on Tuesday that the party would not sanction the Feb. 4 New Hampshire debate planned by MSNBC and the Union-Leader. The committee has faced criticism from the Sanders and O’Malley campaigns for limiting the number of debates to six. Some have speculated that the DNC limited the debates in an attempt to protect Clinton. Fallon addressed that criticism on Wednesday.

“That’s not true at all. Hillary Clinton consistently said she enjoys debating. I think it shows in all the debates. I think without exception she has performed really well at the debates. In the aftermath, everyone says this is really her place to shine because she is so substantive in these forums,” he said on CNN. “Now is an opportunity to put another one on the schedule. It is unclear why Sanders is the lone holdout.”