"A lot of what caused the risk that led to the collapse came from institutions that were not big banks," she told the Des Moines Register.

And when actress Lena Dunham challenged her ties to Wall Street this week, Mrs Clinton said the problem with those who call for breaking up the giant lenders is: "A lot of the problems were not from these traditional banks."

However, in Mrs Clinton's dash through financial topics, she's trying to criticise financial titans enough to satisfy her party while also taking campaign money from bankers. Any soft spot for big banks puts her at odds with the party's left flank. Mr Sanders authored a bill in May to shrink such banks as JPMorgan Chase & Co and Goldman Sachs Group Inc and Ms Warren remains the loudest critic of Wall Street, having introduced a bill to rebuild the Glass-Steagall wall between companies' financial activities that Mrs Clinton's husband breeched as president.

Deflecting blame from the banks also raises the question for Mrs Clinton: What about the crisis woes of firms such as Citigroup Inc, which has long been among her banking supporters? The lender and its employees have been the No.1 contributor to her political career, giving more than $800,000 – even during the period she told Dunham she "took on Wall Street" as a senator from New York. And two of Citigroup's fellows in finance have stepped in as top 10 donors to the Democrat's presidential run: Morgan Stanley and JPMorgan.

Senator Sherrod Brown, the top Democrat on the Banking Committee, has hammered the biggest banks from Capitol Hill and isn't about to let them off the hook for the crisis, even as he said he's "not going to get in a fight with Hillary".