According to Giuliani, Ukrainian officials conspired with the Clinton campaign and the Democratic National Committee to help boost the Democratic nominee’s campaign and damage Trump’s candidacy. No evidence has emerged to support that idea.

In his testimony, Vindman said there was no “factual basis” for such claims. “I am, frankly, unaware of any authoritative basis for Ukranian interference in 2016 elections, based on my knowledge,” he said.

Hill went further, telling lawmakers she had no reason to believe that the intelligence community’s assessment was wrong or that Ukraine interfered in the 2016 election, though she clarified that she was referring only to the government in Kyiv.

Hill appeared frustrated by repeated questions from the Republicans’ lead counsel about a POLITICO article from January 2017, which said a Ukrainian-American working for the DNC had met up with top officials at the Ukrainian embassy to discuss Trump campaign chairman Paul Manafort’s ties to Russia.

“It is a fiction that the Ukrainian government was launching an effort to upend our election, upend our election to mess with our Democratic systems,” Hill testified.

Asked whether a Ukrainian-American might have been interested in “injecting” negative information about Manafort into the press, Hill retorted that the same could be said of the Ukrainian-American operatives Lev Parnas and Igor Fruman, two Giuliani associates “who were also trying to subvert our democracy and who managed to get one of our ambassadors sacked.”

Former White House advisor on Russia, Fiona Hill, arrives on Capitol Hill on Oct. 14 as she is scheduled to testify before congressional lawmakers. | Andrew Harnik/AP Photo

Parnas and Fruman had been lobbying members of Congress and the administration to pressure the State Department into firing U.S. Ambassador to Ukraine Marie Yovanovitch, whose anti-corruption efforts were interfering with Parnas and Fruman’s business interests.

“If you're also trying to peddle an alternative variation of whether the Ukrainians subverted our election, I don't want to be part of that, and I will not be part of it,” Hill said. “What we're dealing with now is a situation where we are at risk of saying that everything that happened in 2016 was a result of Ukraine in some fashion.”

“I'm extremely concerned that this is a rabbit hole that we're all going to go down in between now and the 2020 election, and it will be to all of our detriment,” she added. “And I just want to, if I've done anything, leave a message to you that we should all be greatly concerned about what the Russians intend to do in 2020. And any information that they can provide, you know, that basically deflects our attention away from what they did and what they're planning on doing is very useful to them.”

It wasn’t just Giuliani who has advanced the Ukraine-did-it conspiracy theory. During his July 25 call with Zelensky, Trump mentioned a somewhat garbled version of events while asking his Ukrainian counterpart to also investigate former vice president Joe Biden and his son Hunter.

“I would like you to find out what happened with this whole situation with Ukraine,” Trump told Zelensky, going on to make a convoluted reference to a DNC server that he apparently, and falsely, believes is in Ukraine.

During the 2016 campaign, hackers linked to Russia broke into the DNC’s computer system and released internal emails of discussions between top committee officials.

The publication of the emails, which suggested to some that DNC leaders were conspiring to help Clinton win the Democratic primary over Vermont Sen. Bernie Sanders, led to the resignation of chairwoman Debbie Wasserman-Schultz, cast a pall over the nominating convention and embittered many voters on the left against the party establishment.

The idea that Ukraine was behind the DNC hack may first have been planted in Trump’s mind by Manafort, who pushed the widely debunked theory shortly before the November election, according to FBI documents released last week and first published by BuzzFeed.

The allegation was made by Rick Gates, Manafort’s former deputy, who broke with his boss to testify as part of the Russia probe led by special counsel Robert Mueller.

“Gates recalled Manafort saying the hack was likely carried out by the Ukrainians, not the Russians, which parroted a narrative Kilimnik often supported,” FBI notes say, referring to Konstantin Kilimnik, a Manafort business partner who has been linked to Russian intelligence.

“Kilimnik also opined the hack could have been perpetrated by Russian operatives in Ukraine,” the FBI memo said.

Hill testified to House lawmakers that she had met Kilimnik years earlier, and believed he was a Russian operative—and that Ukraine under its previous president Petro Poroshenko had allowed Kilimnik, who was a witness in the Mueller investigation, to flee to Russia.

“All of my staff thought he was a Russian spy,” she said.