 -- The Italian fiancee of George Papadopoulos offered the first public defense of the embattled former Trump campaign adviser, who in October was revealed as the first campaign adviser to plead guilty and cooperate with the special counsel’s Russia probe.

“George is very loyal to his country,” Simona Mangiante told ABC News chief anchor George Stephanopoulos in an exclusive interview. “He is already on the right side of history. I think he will make a big difference.”

Papadopoulos pleaded guilty to lying to the FBI and has agreed to cooperate with the investigation into Russian interference in the 2016 presidential campaign. He is due to be sentenced in January.

Mangiante said she decided to speak publicly to counter claims from President Donald Trump and his aides that Papadopoulos was, as Trump tweeted, a “young, low level volunteer.” Or in the words of campaign adviser Michael Caputo, a “coffee boy.”

Mangiante said he was far from a bit player in the historic Republican campaign.

“First of all, I would love George to learn how to make a coffee, because it's absolutely out of his skills,” she joked. “George is a remarkable young man with incredible experience in the field of energy and oil policies. This experience led him to get into the campaign and to advise the president at only 28 years old."

Mangiante said Papadopoulos "set up meetings with leaders all over the world” for senior campaign officials. He was “constantly in touch with high-level officials in the campaign,” she added. That included direct communication with now-former senior Trump advisers Steve Bannon and Michael Flynn, Mangiante said, adding that she had seen correspondence supporting the assertion.

Neither Bannon nor an attorney for Flynn responded to a request for comment Thursday.

How close Papadopoulos got to the upper ranks of the campaign remains unclear. White House press secretary Sarah Sanders has said previously that his role was "extremely limited."

"It was a volunteer position," she said in October.

Mangiante said that while she is eager to offer proof that Papadopoulos was a campaign insider, she has been instructed by attorneys to not provide emails or other possible evidence to reporters.

“He never took any initiative, as far as I know, [that was] unauthorized. All the initiatives had [the] blessing of the campaign,” she said.

The story of how Papadopoulos became swept up into the special counsel probe has only begun to emerge into clearer view. His fiancée said she now believes the young energy consultant was manipulated by a European academic who reached out to him after he was named as a member of Trump’s foreign policy team. Both she and Papadopoulos had worked at different times for Professor Joseph Mifsud, then the director of the London Academy of Diplomacy.

Court records filed by special counsel Robert Mueller describe how a professor approached Papadopoulos after learning of his role in the Trump campaign. The court filing does not name the professor, but Mangiante identified him as Mifsud.

The court records describe the professor as someone with “substantial connections to Russian government officials," who said Mifsud told Papadopoulos he could help the young campaign aide obtain “dirt” on Democrat Hillary Clinton that had been obtained by the Russians.

Mangiante said she always had questions about Mifsud’s role because she rarely saw him do the work typical of most professors. He was “opaque,” she said. “It was never clear to me, his role. He doesn't strike me as an academic. He always [was] someone networking [with] people from different governments.”

She said she now believes Mifsud became interested in Papadopoulos “precisely because he was working for Trump.”

But in October, Mifsud acknowledged to the Daily Telegraph that he indeed was the man described in the papers. He also denied any wrongdoing or knowledge of the Clinton emails.

In retrospect, Mangiante told ABC News, it may be that Papadopoulos “didn’t really realize what was going on” when the professor offered to provide him with connections in Russia.

Papadopoulos was arrested by the FBI when he arrived at Dulles International Airport on July 27 and charged under seal. Since that time, she said, he has been cooperating with investigators.

An Italian citizen, Mangiante herself was questioned by agents who wanted to know more about her. She said she was brought to an FBI office in Chicago and asked about her work for Mifsud, about her work as a political aide for the European Parliament in Brussels, and about how she came to meet Papadopoulos. At one point, they asked her if she spoke Russian, she said -- she told ABC News she does not. She received a subpoena in October to appear before a grand jury but did not have to attend, she said, because agents were satisfied by her interview.

“I must say that they have been fair,” she said. “And I was happy to give my contribution.”

Mangiante said she was speaking out now because it has pained her to see her fiancé marginalized by his former campaign colleagues, and to make it clear that he now intends to help his country by cooperating fully.

“He was very brave and decent to take responsibility” for lying to the FBI, she said. “George is very loyal to his country.”

She said she believes he will now have a firm place in history as “the first domino in the Russia investigation.”

ABC News' Alex Hosenball and Michael Del Moro contributed to this report.