Mr. Stone wrote an article for Breitbart News on Aug. 5 attributing the DNC breach to Guccifer 2.0, not Russia, and swapped a handful of direct messages with the persona in the weeks that followed, according to copies of the conversations provided to the Times.

In one of the messages dated Aug. 14, Mr. Stone said he was "delighted" that Twitter had reinstated Guccifer 2.0's account following a brief suspension. Two days later, Mr. Stone again privately messaged the Twitter account and asked for it to retweet a column he had written about the prospects of the 2016 presidential election being "rigged."