Roger Stone, a longtime ally of President Trump, speaks to reporters after appearing before a closed House Intelligence Committee meeting in September 2017. (Kevin Lamarque/Reuters)

In the spring of 2016, longtime political operative Roger Stone had a phone conversation that would later seem prophetic, according to the person on the other end of the line.

Stone, an informal adviser to then-candidate Donald Trump, said he had learned from WikiLeaks founder Julian Assange that his organization had obtained emails that would torment senior Democrats such as John Podesta, then campaign chairman for Democratic presidential candidate Hillary Clinton.

The conversation occurred before it was publicly known that hackers had obtained the emails of Podesta and of the Democratic National Committee, documents that WikiLeaks released in late July and October. The U.S. intelligence community later concluded that the hackers were working for Russia.

The person, who spoke to The Washington Post on the condition of anonymity because of the ongoing federal investigation into Russian campaign interference, is one of two Stone associates who say Stone claimed to have had contact with Assange in 2016.

The Washington Post's Fact Checker took a closer look at Julian Assange's assurance that there is no link between the Russian government and the hacked DNC emails that WikiLeaks released during the 2016 presidential campaign. (Jenny Starrs/The Washington Post)

The second, former Trump adviser Sam Nunberg, said in an interview Monday that Stone told him that he had met with Assange — a conversation Nunberg said investigators for special counsel Robert S. Mueller III recently asked him to describe.

Stone’s possible connection to Assange has been under scrutiny since the 2016 campaign, when he made public claims that he was in contact with the London-based WikiLeaks founder. Since then, Stone has emphatically denied any communication with Assange or advance knowledge of the document dumps by WikiLeaks, which embarrassed Clinton allies and disrupted the 2016 campaign. WikiLeaks and Assange have also said they never communicated with Stone.

Potential contacts with WikiLeaks have been probed by federal investigators examining whether allies of President Trump coordinated with Russians seeking to tilt the 2016 race. The president has repeatedly denied any collusion with Russia.

Peter Carr, a spokesman for Mueller’s office, declined to comment.

Stone, a longtime Trump friend, briefly worked for his presidential campaign in 2015 and then remained in his orbit as an adviser.

In an interview Monday, he again denied that he had any advance notice about the hacked emails or any contact with Assange. He said he only recalled having one conversation with anyone in which he alluded to meeting the WikiLeaks founder — a comment he said he made as a joke to a long-winded Nunberg.

Former Trump advisor and longtime friend Roger Stone discusses his communication with Russian hacker Guccifer 2.0 and Wikileaks founder Julian Assange. (McKenna Ewen,Jorge Ribas/The Washington Post)

“I wish him no ill will, but Sam can manically and persistently call you,” Stone said, recalling that Nunberg had called him on a Friday to ask about his plans for the weekend. “I said, ‘I think I will go to London for the weekend and meet with Julian Assange.’ It was a joke, a throwaway line to get him off the phone. The idea that I would meet with Assange undetected is ridiculous on its face.’ ’’

Stone said that he does not recall any similar conversation with anyone else.

“The allegation that I met with Assange, or asked for a meeting or communicated with Assange, is provably false,” he said, adding that he did not leave the country in 2016.

Through his attorney, Assange — who has been living in the Ecuadoran Embassy in London since 2012 — told The Post in January that he did not meet Stone in spring 2016. His attorney was unable to reach Assange on Monday evening for further comment.

WikiLeaks has denied any contact with the longtime Trump adviser.

“WikiLeaks & Assange have repeatedly confirmed that they have never communicated with Stone,” the organization tweeted in March 2017.

Nunberg told The Post that the questions he was asked by Mueller’s investigators indicated to him that the special counsel is examining statements Stone has made publicly about WikiLeaks.

“Of course they have to investigate this,” he said. “Roger made statements that could be problematic.”

He said he did not recall the exact date when Stone told him that he had met with Assange, adding that he did not take the comment as a joke at the time. He said he was glad to hear Stone told The Post that the remark was made in jest.

“No one connected to the president should be connected with Julian Assange,” he added.

WikiLeaks has come under intense scrutiny from U.S. officials for its distribution of hacked materials. Last year, CIA Director Mike Pompeo said it was “time to call out WikiLeaks for what it really is: a nonstate, hostile intelligence service often abetted by state actors, like Russia.”

In response, Assange said that Pompeo had chosen “to declare war on free speech.”

During the 2016 race, the organization released hacked Democratic emails at two key junctures: A cache of DNC emails landed on the eve of the party’s national nomination convention and a collection of Podesta emails appeared on the same day in October that The Post revealed a tape of Trump speaking about women in lewd terms.

Stone publicly cheered on WikiLeaks during the race, at one point referring to Assange as “my hero.”

On Aug. 8, 2016, in an appearance at the Southwest Broward Republican Organization in Florida, Stone answered a question about what he suspected would be the campaign’s October surprise by saying: “I actually have communicated with Assange. I believe the next tranche of his documents pertain to the Clinton Foundation, but there’s no telling what the October surprise may be.”

He later said he had not meant that he had communicated with Assange directly.

On Aug. 21, Stone tweeted that something grim was looming for Podesta.

“Trust me, it will soon [be] the Podesta’s time in the barrel. #CrookedHillary,” he tweeted.

On Oct. 3, he tweeted: “I have total confidence that @wikileaks and my hero Julian Assange will educate the American people soon #LockHerUp.”

“Payload coming. #Lockthemup,” Stone tweeted on Oct. 5.

Two days later, WikiLeaks published a cache of Podesta’s hacked emails describing internal conflicts within the Clinton Foundation and excerpts of Clinton’s speeches to Wall Street executives.

The release came shortly after The Post revealed the existence of an “Access Hollywood” tape in which Trump described grabbing women by the genitals.

Stone also exchanged private Twitter messages with WikiLeaks that month. In one Oct. 13 exchange, he described himself as a defender of the organization and objected to its “strategy of attacking me,” the Atlantic reported this year. WikiLeaks replied to Stone in a private message that “false claims of association” were being used by Democrats to undermine the group.

Stone answered: “You need to figure out who your friends are.”

Assange and Stone said that the messages prove he did not have any advance knowledge of WikiLeaks’ plans.

“A message telling Roger Stone to cease falsely suggesting contact with WikiLeaks is now the claimed proof that Roger Stone had contact with WikiLeaks — when it proves what I’ve said all along,” Assange tweeted last month.

Stone wrote recently on his website that “only in the current, highly charged atmosphere can a leaked document which is entirely exculpatory and proves that I was not collaborating with WikiLeaks, provoke an ‘AHA’ moment.”

In a September 2017 appearance before the House Intelligence Committee, Stone also vigorously denied he had any foreknowledge of what WikiLeaks would publish or of the hacking of Podesta’s emails.

“Such assertions are conjecture, supposition, projection, and allegations but none of them are facts,” he wrote in a prepared opening statement.

Stone told the committee that his Aug. 21 tweet was meant as a prediction that Podesta’s business activities would come under scrutiny after Paul Manafort was forced to resign from the Trump campaign amid allegations about his work for a pro-Russian party in Ukraine.

Stone acknowledged that some may label him a “dirty trickster,” but he said he does not engage in illegal activities.

“There is one ‘trick’ that is not in my bag,” he told the committee, “and that is treason.”

Rosalind S. Helderman, Ellen Nakashima and Julie Tate contributed to this report.