A longtime outsider in New York State politics has been identified as the link between WikiLeaks and Roger J. Stone Jr., an adviser to Donald J. Trump who appears to have had advance knowledge about hacked emails related to Hillary Clinton’s presidential campaign.

The outsider, Randy Credico, a comedian who has frequently run for office, posted on Twitter on Tuesday that he had received a subpoena requiring him to appear before the House Intelligence Committee next month. The panel is investigating Russian meddling in the 2016 campaign.

Mr. Credico could not be reached on Wednesday for comment.

A person familiar with the House efforts said that Mr. Credico had been identified as the intermediary between Mr. Stone and Julian Assange, the founder of WikiLeaks.