But one senior Democratic operative close to the Clinton campaign said if the former secretary of state gave up doing Wall Street fundraisers she would risk running out of cash in a drawn-out primary.

“Bernie's viral, grass-roots fundraising is not abating, it is increasing,” he said. “Her advantage on Super Tuesday could be in jeopardy if the campaign is in financial straits. Remember President Gephardt? He was poised to win, but ran out of money. If Bernie can maintain a financial advantage going forward it will be a serious problem for Hillary.”

Clinton campaign manager Robby Mook told reporters at a Bloomberg Politics breakfast on Thursday that Sanders, who hauled in $20 million in January, beat the former first lady in the money race for the month. “I recognized in the summer of last year when those first fundraising reports came on that Sen. Sanders was going to raise a lot of money,” Mook said. “I believe he will have the resources to push this campaign well into the spring."

That means Clinton will have to keep shaking the Wall Street money tree.