A federal judge in Washington unsealed heavily redacted court documents on Tuesday that disclosed the existence of the investigation into possible unregistered lobbying and bribery. The people said it concerned efforts by the lawyer for Mr. Kushner, Abbe Lowell, and the fund-raiser, Elliott Broidy, who pleaded guilty in October to a charge related to a different scheme to lobby the Trump administration.

A billionaire real estate developer from the San Francisco area, Sanford Diller, enlisted their help in securing clemency for a Berkeley psychologist, Hugh L. Baras, who had received a 30-month prison sentence on a conviction of tax evasion and improperly claiming Social Security benefits, according to the filing and the people familiar with the case. Under the suspected scheme, Mr. Diller would make “a substantial political contribution” to an unspecified recipient in exchange for the pardon. He died in February 2018, and there is no evidence that the effort continued after his death.