“The impact of the successful 2016 Russian campaign remains evident today,” she said. “Our nation is being torn apart. Truth is questioned. Our highly professional and expert career foreign service is being undermined.”

Hill, who was the top Russia hand on the National Security Council until July, warned that Moscow’s “ security services and their proxies have geared up to repeat their interference in the 2020 election.”

Hill’s appearance before the House Intelligence Committee comes as Democrats are taking what may be their final shot to buttress their case that Trump abused his power by pressuring Ukraine, through Giuliani, to investigate his political rivals.

Lawmakers leading the impeachment inquiry say they are more confident than ever they have clinched their case against Trump — while Republicans continue to assert there is no direct evidence implicating the president in a Ukraine scheme.

On Thursday, investigators turned to Hill to amplify her account as a White House insider who attended key meetings on Ukraine and reported her concerns about Giuliani’s efforts to a superior. Giuliani, Hill said, was “clearly putting forward issues and ideas that would come back to haunt us.”

“And, in fact, I think that’s where we are today,” Hill added.

Sitting alongside Hill was David Holmes, a minor player in the inquiry but one who supplied key evidence. Holmes overheard a phone call on July 26 between Trump and Gordon Sondland, the U.S. ambassador to the European Union, during which Trump audibly asked about the status of his desired investigation targeting former Vice President Joe Biden.

“Of course the president is pressing for a Biden investigation before he’ll do these things the Ukrainians want,” Holmes said, adding that he and his colleagues at the embassy “agreed it was obvious what the president was asking for.”

Republican lawmakers sought to poke holes in Holmes’ account, noting that the Trump-Sondland phone call was not revealed until last week. And Trump pushed back against Holmes Thursday morning as he was reading his opening statement.

“Never have I been watching a person making a call, which was not on speakerphone, and been able to hear or understand a conversation,” Trump wrote on Twitter. “I’ve even tried, but to no avail.”

Holmes defended his recollection of the encounter, saying it was memorable even though he did not take notes about it at the time.

“This was a very distinctive experience,” Holmes said under questioning Thursday. “Very colorful language was used. They were directly addressing something I had been working on for weeks, months.”

Neither witness was expected to produce the type of testimony that Sondland provided Wednesday, when he told lawmakers that Trump, through Giuliani, had authorized a quid pro quo with Ukraine, denying the country’s new president a White House meeting until he announced an investigation targeting Biden and his son Hunter.

Sondland also indicated that a slew of senior officials knew about the effort, including acting White House chief of staff Mick Mulvaney, Secretary of State Mike Pompeo and Energy Secretary Rick Perry. Pompeo and Perry on Wednesday pushed back on Sondland’s claim.

Hill’s closed-door testimony represented a crucial break for Democrats in the nascent stages of the investigation. She revealed that her boss, former national security adviser John Bolton, worried about a “drug deal” that Mulvaney and Sondland were allegedly involved in, referring to a Ukraine pressure campaign. He also called Giuliani a “hand grenade who’s going to blow everybody up” over his efforts to smear Yovanovitch, according to Hill.

Trump removed Yovanovitch from her post in May and attacked her during a phone call with Ukraine’s newly elected president, Volodymyr Zelensky, on July 25.

Hill also testified about Sondland’s conduct, alleging that he attended meetings about Ukraine that were not in his purview. Hill said she confronted him after a July 10 White House meeting during which Sondland raised the prospect of Trump’s investigations directly with Ukrainian officials.

“I took it to mean investigations for a meeting,” Hill said Thursday, echoing Sondland’s view that a Trump-Zelensky meeting at the White House was conditioned on Ukraine announcing Trump’s desired investigations. Republicans argued Wednesday that Sondland was an unreliable witness who overstated his relationship with the president.

She later told lawmakers that Sondland was “involved in a domestic political errand,” while she and her NSC colleagues were “involved in national security foreign policy.”

“I said to him... I think this is all going to blow up. And here we are,” Hill added.

Holmes, meanwhile, went into detail about the phone call between Trump and Sondland that he overheard. Holmes said he was with Sondland at a restaurant in Kyiv, and Trump asked Sondland about the status of “the investigations.” According to Holmes, Sondland replied that the Ukrainians were “gonna do it,” and that Zelensky “loves your ass.”

Holmes also said it was possible that the Russians intercepted the phone call, which took place at an outdoor cafe on an unsecure cell phone. According to Holmes, Sondland told him that Trump only cares about “‘big stuff’ that benefits the president, like the ‘Biden investigation’ that Giuliani was pushing.”

Sondland said Wednesday he had no reason to doubt Holmes’ account, but he could not recall specifically mentioning the Bidens.

Daniel Lippman contributed to this report.

