Alexander Nix, who heads a controversial data-analytics firm that worked for President Donald Trump’s campaign, wrote in an email last year that he reached out to WikiLeaks founder Julian Assange about Hillary Clinton’s missing 33,000 emails.

On Wednesday, Assange confirmed that such an exchange took place.

Nix, who heads Cambridge Analytica, told a third party that he reached out to Assange about his firm somehow helping the WikiLeaks editor release Clinton’s missing emails, according to two sources familiar with a congressional investigation into interactions between Trump associates and the Kremlin. (CNN later reported Cambridge backer Rebekah Mercer was one of the email's recipients.) Those sources also relayed that, according to Nix’s email, Assange told the Cambridge Analytica CEO that he didn’t want his help, and preferred to do the work on his own.

The interchange between Nix—whose company made millions from the Trump campaign—and Assange represents the closest known connection between Trump’s campaign and Wikileaks.

Cambridge Analytica did not provide comment for this story by press time. But after publication, Assange provided this statement to The Daily Beast: ”We can confirm an approach by Cambridge Analytica and can confirm that it was rejected by WikiLeaks.”

Nobody has published the 33,000 emails that were deleted from the personal email server Hillary Clinton used while she was secretary of State.

“It’s not at all clear that anybody hacked Clinton’s emails or has them,” said one of the sources familiar with the investigation.

Those 33,000 messages were a central focus of Trump and his allies during the campaign. At least one Republican operative tried to recruit hackers to obtain those emails, according to The Wall Street Journal. And at a press conference on July 27, 2016, while the Democratic National Convention was underway, Trump—then the Republican nominee—said he hoped the Kremlin would recover those emails.

“Russia, if you’re listening, I hope you’ll be able to find the 30,000 emails that are missing,” he said.

And on the campaign trail, Trump praised WikiLeaks and tweeted about its findings. Politifact calculated that he mentioned the site about 137 times during the campaign.

“ If the claims are true, this would be the closest known connection between Trump’s campaign and Wikileaks. ”

“I love WikiLeaks!” he proclaimed at a rally on Oct. 10, shortly after the site began publishing emails hacked from Hillary Clinton campaign chairman John Podesta.

By April, Trump’s CIA director was calling WikiLeaks a tool of Kremlin spies and the equivalent of a “hostile intelligence service.”

Roger Stone, a longtime adviser to Trump, was in touch with Assange through an intermediary. The House Intelligence Committee is pushing Stone to share the identity of that intermediary with them. So far, he has not complied.

Robert and Rebekah Mercer, a billionaire father-daughter duo that spent big to boost Trump’s presidential candidacy, are major investors in Cambridge Analytica. Robert Mercer co-manages a hedge fund that drew scrutiny from congressional investigators in 2014 for using questionable banking tactics to allegedly dodge paying upward of $7 billion in taxes. Steve Bannon, formerly a senior White House aide, was on the company’s board before he joined the White House. He has worked with the Mercers on multiple conservative projects, and Bloomberg News reported he previously had holdings in Cambridge Analytica valued at between $1 million and $5 million.

On Wednesday afternoon, Trump campaign executive director Michael Glassner tried to downplay the role Cambridge Analytica played during the election, stating that the Republican National Committee [RNC] was its “main source” for data analytics.

After Trump secured the GOP nomination, Glassner said in a statement: “We were proud to have worked with the RNC and its data experts and relied on them as our main source for data analytics. ... Any claims that voter data from any other source played a key role in the victory are false.”

But FEC data contradicted Glassner. According to the campaign’s own FEC filings, the Trump campaign paid Cambridge Analytica $5.9 million from July 29, 2016—a week after Trump formally accepted the Republican Party’s presidential nomination in Cleveland—to December 12, 2016. Brad Parscale, the campaign’s digital director, told the Wall Street Journal that the “psychographic” firm’s invoices is “mislabeled” in the FEC filing but he didn't elaborate how or why.

A Republican digital strategist who worked with Cambridge Analytica during the 2016 campaign told The Daily Beast that Nix should not be viewed as a reliable narrator.

“Alexander Nix is not credible at all,” the strategist said. “He is a consummate salesman, and there are numerous instances already out in the public record where he made claims that were not just factually wrong—they were total fabrications.”

The source added that this doesn’t mean Nix didn’t reach out to Assange.

“I wouldn’t put it past him, if you consider every other thing that he’s done, every other way that he’s conducted business,” the strategist added. “I absolutely can see him reaching out and making an inquiry, hoping to find another way that Cambridge could become the heroes.”

The source made these statements before Assange publicly admitted the dialogue with Nix.

Update: This report has been updated to include Assange and the Trump campaign’s comments.