Hillary Clinton’s top adviser suggested on Tuesday evening that Donald Trump’s campaign had advance knowledge of the leak of internal Democratic emails that he said were obtained by Russian hackers.

It was an extraordinary claim—presented with only circumstantial evidence—that further raises the specter of foreign meddling in the American election.

“I’ve been involved in politics for nearly five decades. And this definitely is the first campaign that I’ve been involved with in which I’ve had to tangle with Russian intelligence agencies,” said Clinton’s campaign chairman John Podesta. “Who seem to be doing everything they can on behalf of our opponent.”

Since Friday the website Wikileaks has published thousands of hacked personal emails from Podesta’s account that have become fodder for Trump attacks against Clinton. U.S. intelligence officials and the White House have openly accused Russia of meddling in the election by hacking the Democratic National Committee.

Podesta said on Tuesday that the Trump campaign may have had advance knowledge of the leak. Particularly suspect, Podesta said, is Trump’s ally, provocateur and political operative, Roger Stone, who has confirmed he was in contact with Wikileaks’ Julian Assange. The founder of Wikileaks is a fugitive who has been openly critical of Clinton.

“I think it is a reasonable assumption to, or at least a reasonable conclusion, that Mr. Stone had advance warning, and the Trump campaign had advance warning about what Assange was going to do,” said Podesta, who did not confirm the authenticity of the leaked emails.

Stone has delivered enigmatic predictions on Twitter that Assange will “expose” Clinton who will be “done” after an undefined Wikileaks action. He told the Associated Press that Podesta’s accusations were “categorically false.” Podesta said he was in contact with the FBI, which is investigating the hack of his emails.

Trump has repeatedly praised Russian President Vladimir Putin, saying that the authoritarian head of state is a “strong leader.” The Republican nominee encouraged Russia in a rally earlier this year to continue hacking Democratic Party emails shortly after a slew of internal party communications were released.

The Clinton campaign has said for weeks that Russia is attempting to tilt the U.S. election this year in favor of Trump. The mountain of hacked and leaked Democratic emails—which American security officials have traced back to Russia—suggest that Russia wants Trump to win in November, the campaign has claimed.

“We have never in the history of our country been in a situation where an adversary, a foreign power, is working so hard to influence the outcome of the election. And believe me, they’re not doing it to get me elected. They’re doing it to try to influence the election for Donald Trump,” Clinton said at the debate on Sunday.

Trump countered by arguing that it wasn’t clear that Russia was to blame.

“But I notice, anytime anything wrong happens, they like to say the Russians are — she doesn’t know if it’s the Russians doing the hacking,” he said at the debate. “Maybe there is no hacking. But they always blame Russia. And the reason they blame Russia because they think they’re trying to tarnish me with Russia.”

According to American security officials, there’s no direct evidence that Russia is seeking to steer the election in favor of either Clinton or Trump. But Russian hackers are behind the recent disruptions, intelligence officers say, in an attempt to undermine the legitimacy of American democracy.

Read More: How Russia Wants to Undermine the U.S. Election

The emails that Wikileaks has published are not related to the emails Clinton herself sent and received during her time at the State Department between 2009 and 2013. They are mostly internal communications between Podesta and other top Clinton advisers.

So far, the hacked emails do not show any wrongdoing by Clinton or her campaign. One reveals partial transcripts from her paid speeches after she left the State Department. Another show that Clinton press secretary Brian Fallon had notice from the Justice Department—where he formerly worked—of a hearing date to schedule Clinton’s email release, but there is no evidence of impropriety.

The Wikileaks emails also show Clinton aides debating campaign strategy: how to formulate messaging against Vermont Sen. Bernie Sanders during the Democratic primary, how Clinton should defend herself against attacks over her private email server during her time as Secretary of State, among other matters.

Podesta told reporters on Tuesday that there was circumstantial evidence that Stone knew about the hacked emails before they were published. In August, Stone tweeted cryptically that Podesta would soon be “in the barrel.”

Meanwhile, Trump has been downplaying Russia’s aggression in Syria and Ukraine, Podesta said.

“So he’s either willfully ignoring the information that’s coming from the highest reaches of the US intelligence community, or he is, as or former acting CIA director Mike Morell said, an unwitting agent of the Russian Federation,” said Podesta.

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