WASHINGTON — Roger J. Stone Jr., a longtime informal adviser to President Trump who has spent decades plying the dark arts of scandal-mongering and dirty tricks to help influence American political campaigns, was indicted Friday in the special counsel investigation.

Mr. Stone was charged with seven counts, including obstruction of an official proceeding, making false statements and witness tampering, according to the special counsel’s office.

The indictment is the first public move in months by the special counsel, Robert S. Mueller III, who is investigating Russia’s interference in the 2016 election and possible coordination with Trump associates.

[Read the indictment.]

Mr. Stone and his lawyer could not immediately be reached for comment.

Mr. Stone, a self-described dirty trickster who began his career as a campaign aide for Richard M. Nixon and has a tattoo of Nixon on his back, has long maintained that he had no connection to Russia’s attempts to disrupt the 2016 presidential election. He sometimes seemed to taunt American law enforcement agencies, daring them to find hard evidence to link him to the Russian meddling campaign.