To the consternation of many in the finance sector, the choice of the next Fed chair is not the only issue affecting their business on which Mr Brown is making his mark.

With a Republican senator, David Vitter, he crafted a bill this year forcing big banks to take on extra capital; in recent weeks, he has been holding hearings pushing regulators to take a tougher line on banks in the commodities business.

“He has arguably become one of the leading voices on banking policy in Washington,” said Chris Krueger, of Guggenheim Securities, in Washington.