But at a minimum, that would require evidence that the Trump campaign knew that WikiLeaks was trying to damage Hillary Clinton’s candidacy, agreed with that objective and engaged in overt acts to further the scheme.

“Two or more people have to agree to do something that the law forbids, and at least one of them has to take a step to further the conspiracy — an overt act,” said Chuck Rosenberg, a former United States attorney and senior F.B.I. official.

What might constitute an “overt act”? If Trump campaign officials coordinated with Julian Assange, the organization’s founder, on the timing and content of the document releases in an effort to maximize the damage to the Clinton campaign, that might qualify. But Mr. Mueller has offered no evidence of that.

Will charges come later?

Maybe. Mr. Rosenberg cautioned against viewing Mr. Stone’s indictment as the final word on whether the Trump campaign did or did not conspire with WikiLeaks. “I wouldn’t take from the fact that they didn’t charge it that they can’t charge it or that they won’t charge it,” he said.

The special counsel has mounted two criminal cases claiming illegal schemes to tilt the election results, both against Russians. Legal experts cited those cases as possible templates for what a conspiracy case involving the Trump campaign might look like, assuming the evidence existed to bring one.

Thirteen Russians and three Russian companies were accused of conspiring to defraud the United States by illegally influencing the presidential election. That indictment said the Russians mounted an illicit social media campaign aimed at sowing political discord, undercutting Mrs. Clinton and promoting Mr. Trump. Their activities were illegal because foreigners cannot spend money to influence American elections or engage in political activity in the United States without registering with the Justice Department.

In the other case, Mr. Mueller charged 12 Russian military officers with hacking into Democratic computers and releasing tens of thousands of stolen documents, using WikiLeaks and other means. That case alleged a conspiracy to commit computer crimes.