Gov. Eliot Spitzer was a client of a high-end prostitution ring broken up last week by federal authorities, according to law enforcement officials, a development that threatened to end his career and turned the state’s political world upside down. Mr. Spitzer’s involvement with the prostitution operation came to light in court papers filed last week, the officials said, as federal prosecutors charged four people with operating the service, Emperor’s Club V.I.P. Mr. Spitzer was caught on a federal wiretap discussing payments and arranging to meet a prostitute in a Washington hotel room last month. The affidavit, which did not identify Mr. Spitzer by name, indicated that he had used the prostitution service before, although it was not clear how often. In a wiretapped conversation after the encounter, the prostitute, Kristen, called her booker to inform her that the session had gone well, and that she did not find the client “difficult,†as other prostitutes apparently had, according to the affidavit. The booker responds that he, in an apparent reference to Client 9, sometimes asks the women “to do things that, like, you might not think were safe.â€