Wall Street's nightmare: President Elizabeth Warren

And the fear is not only that Warren, who channels an increasingly popular strain of Occupy Wall Street-style anti-corporatism, might win. That is viewed by many political analysts as a slim possibility. It is also that a Warren candidacy, and even the threat of one, would push Clinton to the left in the primaries and revive arguments about breaking up the nation’s largest banks, raising taxes on the wealthy and otherwise stoking populist anger that is likely to also play a big role in the Republican primaries.

“The nightmare scenario for banks is to hear these arguments from a candidate on the far left and on the far right,” said Jaret Seiberg, a financial services industry analyst at Guggenheim Partners. “Suddenly you have Elizabeth Warren screaming about ‘too big to fail’ on one side and Rand Paul screaming about it on the other side and then candidates in the middle are forced to weigh in.”

A spokesperson for Warren declined to comment on whether she would consider a presidential bid against Clinton, though Warren has previously said she has no plans to run. People close to Warren note that she signed a letter from female Democratic senators urging Clinton to run in 2016. And Warren associates, mindful of any appearance of creating the narrative of a Warren-for-president campaign, have corresponded with Clinton associates to stress that they didn’t fuel the New Republic story by Noam Scheiber.