The biggest share of the legal payments revealed on Sunday by Mr. Trump’s campaign and the joint committees it formed with the Republican Party — $830,000 — went to Jones Day, the law firm representing the campaign in connection with the investigations.

In May, the campaign sent a letter to current and former staff members instructing them to retain documents related to the campaign. The letter, a copy of which was obtained by The New York Times, indicated that Jones Day lawyers “will be responsible for collecting, reviewing and, if appropriate, producing materials to the congressional committees and the special counsel.”

The campaign committee also paid nearly $238,000 in July and August to the offices of the New York lawyer Alan S. Futerfas, who is representing the president’s son Donald Trump Jr. in the investigations.