With a populist message that promises to rein in corporate excess, Ms. Warren has been facing more hostility from the finance industry than any other candidate. From corporate boardrooms to breakfast meetings, investor conferences to charity galas, Ms. Warren’s rise in the Democratic primary polls is rattling bankers, investors and their affluent clients, who see in the Massachusetts senator a formidable opponent who could damage not only their industry but their way of life.

Mr. Epstein, who was charged this month with sex trafficking of teenage girls, liked to portray himself as a financial wizard, someone whose business and investing acumen made him indispensable to corporate executives and other leaders. But there is little evidence to support that notion. The financial services that Mr. Epstein dispensed appear to have been mostly pedestrian, and his list of clients small.Mr. Epstein nonetheless managed to affix himself to a handful of prominent Wall Street veterans, including Mr. Staley, who is now chief executive of the British bank Barclays.

White House officials insisted that there was no single factor behind the departure of Mr. Cohn, who heads the National Economic Council. But his decision to leave came as he seemed poised to lose an internal struggle over Mr. Trump’s plan to impose large tariffs on steel and aluminum imports. Mr. Cohn had warned last week that he might resign if Mr. Trump followed through with the tariffs, which Mr. Cohn had lobbied against internally.