The original FBI counterintelligence probe was launched in part because a Trump campaign adviser was said to have told an Australian diplomat that Russia had emails that could embarrass Democrats, and in July 2016, private Democratic messages thought to have been hacked by Russia began appearing online.

Mueller also is in possession of information from Facebook about politically themed advertisements bought through Russian accounts.

Legal analysts have said that one charge Mueller might pursue would be a conspiracy to violate the Computer Fraud and Abuse Act, if he can demonstrate that members of Trump’s team conspired in Russia’s hacking effort to influence the election.