WASHINGTON — An associate of the former Trump campaign adviser Roger J. Stone Jr. released documents on Tuesday showing that as the presidential campaign heated up in the summer of 2016, Mr. Stone tried to dispatch him to find out what information WikiLeaks had that could prove damaging to Hillary Clinton’s campaign.

The associate, Jerome Corsi, said in an interview that he might be indicted on a charge of lying to federal investigators because he told them that he refused Mr. Stone’s request when in fact he passed it on to an intermediary. He said he had refused a plea deal offered by the office of the special counsel, Robert S. Mueller III, because he did not intentionally lie, but merely forgot events of more than two years ago.

Mr. Corsi’s dealings with Mr. Mueller’s prosecutors have caused alarm among the president’s legal team, who were informed of developments by Mr. Corsi’s lawyer. President Trump’s lawyers were especially troubled by a draft statement of offense against Mr. Corsi that was passed on to them, according to people familiar with the situation. In it, prosecutors claimed that Mr. Corsi understood that Mr. Stone was “in regular contact with senior members of the Trump campaign, including with then-candidate Donald J. Trump” when he asked Mr. Corsi in late July 2016 to “get to” Julian Assange, the founder of WikiLeaks.

The reference to Mr. Trump coincided with other events that so disturbed the president’s lawyers that they delayed turning in his responses to written questions after negotiating over them with the special counsel for nearly a year. At roughly the same time, the Justice Department inadvertently released a secret criminal complaint against Mr. Assange and Mr. Trump’s legal team learned that prosecutors were accusing Paul Manafort, Mr. Trump’s campaign chairman, of lying. Only after Mr. Mueller’s team reassured Mr. Trump’s lawyers that they were not trying to lure the president into a trap did they forward his answers on Nov. 20.