WASHINGTON — An associate traveling with Rudy Giuliani in Ukraine this week has voiced an unusual theory for why he may not be able to return to the United States: “Soros people,” he says, are working to discredit him and may block his visa.

Andriy Telizhenko, a former Ukrainian diplomat who has alleged Ukraine’s government conspired with Democrats in 2016, said he’s been told that people associated with liberal megadonor George Soros, including former Ukrainian politicians, are working against him — possibly because he’s helping Giuliani continue investigating President Donald Trump’s political opponents and undermine the credibility of the House impeachment inquiry.

“Soros people are trying to discredit my reputation with lies and then will try to block me,” he said in a text message to NBC News from Kyiv. He did not name any individually or provide proof other than to say some were writing about him online.

It was far from the first time that Soros, a billionaire philanthropist and a frequent target of conspiracies about Jews controlling the world, has popped up as part of a conspiracy theory portraying Soros as using Ukraine as a playing field to undermine Trump’s campaign. The president’s allies and other Republicans have been working to tie Soros to nefarious plots to intervene in U.S. affairs for a full year — or even longer.

When Fiona Hill, then a National Security Council official, started hearing early in 2019 about a smear campaign against a colleague in Ukraine invoking Soros, she had a sinking feeling: She’d heard this before.

A similar conspiracy theory about Soros had been lobbed against Hill during her first year as Trump’s top adviser on Russia and Europe. That’s when Hill says a former Republican congressman from Florida tried to get the vice president’s office to get rid of her — “to have me fired for being a Soros mole in the White House,” she told Congress.

That former congressman, Connie Mack IV, now a lobbyist, confirms he met in 2017 with the vice president’s national security adviser about Hill’s “conflict of interest” stemming from what he alleged are her ties to Soros, a frequent target of conspiracies about Jews controlling the world. Hill testified that the allegation was “frankly an anti-Semitic conspiracy theory.”

“I think that was a clever way to not answer the question and to force the conversation in a different direction,” Mack said in an interview with NBC News. “She never once addressed whether or not she has any connection to Soros, instead blaming people that want to raise the issue as being anti-Semitic, which is devious in my opinion.”

In 2017, Mack’s client was Viktor Orban, Hungary’s nationalist prime minister who has vilified Soros as part of his bid to stifle dissent. But Soros' name would later emerge again and again in the events at the heart of the impeachment inquiry.

A successful campaign to oust Marie Yovanovitch as the U.S. ambassador to Ukraine by Trump's personal attorney, Rudy Giuliani, and two now-indicted associates was galvanized by accusations that Yovanovitch protected Soros’ efforts. Those accusations originated in an opinion article by John Solomon in the “The Hill,” which, according to documents given to Congress, he coordinated with one of the indicted Giuliani associates and with two pro-Trump lawyers, Victoria Toensing and Joe diGenova.

Last month, as the impeachment probe unfolded, diGenova told Fox News that Soros “wants to run Ukraine” and “controls a very large part” of the U.S. diplomatic corps, along with FBI agents in Ukraine and elsewhere. Giuliani falsely told The Washington Post in September that Yovanovitch was “now working for Soros.” In fact, she is still a U.S. government employee.

Giuliani also told CNN that month that an anti-corruption nonprofit in Ukraine that took funding from a Soros philanthropy had fabricated evidence against former Trump campaign chairman Paul Manafort. He later told Fox News’ Sean Hannity that the Ukrainians had “brought me substantial evidence of Ukrainian collusion with Hillary Clinton, the D.N.C., George Soros, George Soros' company.”

“They put it in my lap,” he said.

And last month, a photo that purportedly showed the whistleblower who outed Trump’s call with the Ukrainian leader went viral, tweeted out by Rep. Steve King, R-Iowa. It turned out to be a photo of Soros’ son.

Aryeh Tuchman of the Anti-Defamation League, which tracks anti-Semitism, said the notion of a secret cabal of Jews plotting to take over countries or the world to advance their own interests has been prevalent for hundreds of years, playing a role in pre-Holocaust propaganda. Although he said not all criticisms of wealthy Jews such as Soros are necessarily anti-Semitic, they’re likely to be perceived that way by anti-Semites.

“An extremist, a hardcore anti-Semite who hears a mainstream individual, a pundit, a politician, anyone articulating these sort of conspiracy theories, they may be emboldened, they may feel that their anti-Semitic ideology has been confirmed,” Tuchman said. “This may energize them in a way they may not have been.”

In Hill’s case, it began with Mack pushing the theory, to journalists and lawmakers, that Hill was driving “hostility towards Hungary” within the Trump administration because of what he said were her ties to Soros: her work for a European civil society foundation that had received funding from Soros philanthropies, and her former role on an unpaid advisory board for a Soros-linked institute.

In an interview, Mack said he’d found a book on the internet that said that Hill had attended Soros’ wedding, although he couldn’t recall the name of the book offhand and an internet search did not turn one up. Hill’s attorney said the assertion was false — she wasn’t at the wedding.

Hill said she starting getting death threats when Mack’s allegations made it to Roger Stone, a Trump associate who was convicted last month of lying to Congress, as well as the conspiracy theorist Alex Jones and his far-right channel, InfoWars. In lobbying documents about Hill, Mack said he was shining “a light on the far-reaching network of George Soros in order to continually degrade his international influence.”

“There is clearly a conflict of interest,” Mack said. Orban, his client, had been working to oust a Soros-founded university from Budapest.

Mack said he made that case to Vice President Mike Pence’s national security adviser at the time, Andrea Thompson. Hill, testifying in the impeachment hearings, said Mack had used the InfoWars article “as an exhibit” to buttress his claim that she was “a Soros mole.”

Thompson declined to comment. But Lee Wolosky, Hill’s attorney, said any work Hill had done at Soros-linked entities had been promoting a “fundamentally American” interest: advancing democracy and civil society in the former Soviet Union.

“That is a core American value and has been a bedrock of our foreign policy for decades,” Wolosky said. In a swipe at Mack, he added, “taking money from foreign governments to promote the agendas of autocrats in Washington is fundamentally un-American.”

In the Ukraine saga, the theory of a nefarious Soros plot to undermine Trump centers on an anti-corruption nonprofit in Ukraine called AntAc, which received the majority of its funding from the U.S. government but had also taken funding from Soros philanthropies.

Giuliani and others accused the group, without evidence, of hiring a “crooked FBI agent” to help develop “dirty information” on Manafort, who was later convicted in the U.S. of financial crimes related to his work in Ukraine. The key disclosure that precipitated his downfall — the so-called black ledger showing off-the-books payments from Ukraine’s former pro-Russian government — did not emanate from AntAc but from a Ukrainian law enforcement agency and a Ukrainian politician.

Telizhenko, the former Ukrainian diplomat, has long alleged that AntAc worked on Soros’ behalf in trying to get rid of former Ukrainian Prosecutor General Victor Shokin, Telizhenko’s former boss. Shokin is the prosecutor who Republicans allege that former Vice President Joe Biden got fired to protect his son Hunter Biden’s natural gas company from scrutiny. Telizhenko in 2017 alleged that during the 2016 campaign, Ukrainian embassy officials in Washington coordinated with a Democratic National Committee operative to dig up information linking Trump's campaign to Russia.

Yovanovitch’s place in the conspiracy theory stems from unproven allegations by Giuliani associates that she worked to quash a Ukrainian government investigation into AntAc, in order to protect Soros’ work hurting Trump and helping Hillary Clinton. Hill, in her testimony, compared the smear campaign to “the new Protocols of the Elders of Zion.”

A Soros spokesman referred questions to his philanthropy network, Open Society Foundations. Laura Silber, the group’s chief communications officer, said Soros, who is Hungarian American and a Holocaust survivor, has been funding projects in Europe for decades to fight corruption and promote the transition to democracy in former Soviet states.

“The anti-Semitic conspiracy theories and false allegations espoused by Rudolph Giuliani and his cronies are aimed at fomenting hatred, undermining democracy,” Silber said, “as well as distracting from the impeachment process and the critically important national security and Constitutional questions before Congress.”