(CNN) Hillary Clinton has at least one thing to be thankful for: Superdelegates.
"That is her only true firewall," an adviser glumly said Wednesday in the wake of a humbling New Hampshire defeat that has shaken the confidence of the candidate and the campaign.
For Clinton, who remained out of public view Wednesday, it's a day of assessing strategy, reassuring donors and planning for how to confront Bernie Sanders at their debate on Thursday in Milwaukee.
Campaign chairman John Podesta is scheduled to speak to top donors on a late-afternoon conference call about the state of the campaign, two people familiar with the call said, describing it as an opportunity to put supporters at ease and urge them to work harder in hopes of competing with Sanders' fundraising juggernaut.
Superdelegates are party officials who are intended to help play an oversized role in the nominating process -- to protect the party. That's what is at play here. Of course, we all remember how dozens of Superdelegates jumped ship in 2008 and went running toward Obama after he won their districts. (Paging John Lewis!)
There is also deep anxiety about Clinton's message. One top donor watched her Tuesday night speech with alarm, telling CNN: "It's all about her. Why is it always about her?"
The campaign is operating on two fronts: trying to improve Clinton's ability to channel the frustration in the electorate and drawing more scrutiny on Sanders' record. For weeks, the campaign research team has been scouring away at his long record in Vermont and Washington and intends to start a "far more aggressive" approach to Sanders, one aide said.
For all the talk about a campaign shakeup, several people close to the organization said Clinton was eying someone to coordinate message, so their television advertising and campaign message were the same or complimentary, rather than competing.
The first day of the next phase of the campaign is Thursday night in Milwaukee on the debate stage. But campaign aides say they know they have to hunker down -- as Clinton "guts it out."
"Only she can fix this," one adviser said.