Roger Stone, one of Trump's longtime allies who advised him informally during the 2016 campaign, is set to testify before the House intelligence committee later this month in a closed hearing.

Why it matters: Stone has said he has communicated with Guccifer 2.0, the hacker believed to be a front for Russian intelligence that's taken credit for hacking into the Democratic National Committee.

Stone has said he wants the transcripts of his appearance to be immediately released and is calling for an open hearing even though the panel's business is usually closed.