Turkey had mounted an elaborate influence campaign in Washington to deal with Halkbank. It predated Mr. Trump’s election but came to encompass a broad cast of players, including Rudolph W. Giuliani, the former New York mayor; Michael T. Flynn, Mr. Trump’s first national security adviser; and Brian D. Ballard, a lobbyist and fund-raiser for the president.
After senior Turkish government officials lobbied Treasury Secretary Steven Mnuchin and Mr. Trump, Mr. Mnuchin pressed the Justice Department not to impose too large a fine on Halkbank because Turkey could not afford it, two federal officials said. Mr. Mnuchin’s office declined to comment on Halkbank but added that the Treasury and Justice Departments “routinely consult and coordinate” on sanctions cases and fines.
Mr. Bolton and others said they could not fully explain why Mr. Trump seemed so determined to please Mr. Erdogan.