At the time, the row between a top White House national security official and the US ambassador to the EU appeared to be a simple matter of miscommunication.
Fiona Hill, the senior director for European and Russia affairs on the National Security Council, said on Thursday she had been “angry” with Gordon Sondland, the envoy, for not co-ordinating with her on Ukraine policy.
After weeks of private and public impeachment hearings, including Mr Sondland’s testimony on Wednesday, Ms Hill told Congress she had something of an epiphany about their White House argument in July, shortly before she left her post.
“He was being involved in a domestic political errand, and we were being involved in national security foreign policy, and those two things had just diverged,” she testified, in what could be the last hearing before a House vote on impeaching Donald Trump.
“I did say to him, Ambassador Sondland, Gordon, ‘I think this is all going to blow up’, and here we are,” she added.
The comments were the latest evidence of an irregular diplomatic channel involving senior officials and Rudy Giuliani, the president’s private attorney, that aimed to secure announcements of investigations in Ukraine that would benefit Mr Trump personally.
The channel, which included Mr Sondland, has been a key point of contention in the impeachment hearings and a vital part of the story Democrats have attempted to tell the American public as they attempt to build support for the removal of Mr Trump.
Mr Trump is accused of seeking a quid pro quo with Ukraine by withholding congressionally approved military aid and a coveted White House meeting. In return, Mr Trump wanted Volodymyr Zelensky, the newly elected president of Ukraine, to announce two probes that would help him politically in the US, several witnesses have testified.
One of the desired announcements concerned alleged 2016 election meddling by Ukraine, while the other related to Burisma, a Ukrainian energy company whose board members included the son of Joe Biden, the former vice-president.
In an explosive appearance on Wednesday, Mr Sondland became the first member of Mr Trump’s team to acknowledge a quid pro quo — involving the Oval Office meeting for Mr Zelensky — and said he had acted on the US president’s orders when he pressed Kyiv for the probes.
Mr Trump has denied any quid pro quo, saying he wanted nothing from the Ukrainian president other than for him to “do the right thing”.
Republicans have argued that Mr Trump had a legitimate interest in uncovering the truth about Ukraine’s role in the 2016 election. Mr Sondland and another key witness, Kurt Volker, have said they did not know Burisma was code for the Bidens.
Ms Hill’s testimony on Thursday undercut both of those positions. The British-born national security official called the idea that Ukraine meddled in 2016 a “fictional narrative that has been perpetrated and propagated by the Russian security services themselves”.
She noted that many officials from US allies across the world, including Ukraine, had made negative comments about Mr Trump during the 2016 campaign, but sought to distinguish that from the top-down campaign of misinformation launched by the Russians.
“I don’t think those two things are exactly the same,” she said, even as she agreed that Mr Trump had every right to feel “aggrieved” about the fact that some foreign officials had publicly backed his rival in 2016, Hillary Clinton.
She also said it was plain that Mr Trump’s desire for an investigation into Burisma related to the fact that it could damage Mr Biden, a potential rival in the 2020 election.
“It was clear that Burisma was code for the Bidens, because Giuliani was laying it out there,” she testified, referencing public statements by Mr Giuliani.
She made the point more directly in regard to Mr Sondland: “It’s not credible to me at all that he was oblivious to this.”
David Holmes, a US diplomat in Kyiv who testified alongside Ms Hill, agreed, telling the committee: “It was obvious what the president was pressing for.”
The public hearing, the seventh so far, may be the last. Several senior administration officials central to the event at issue have refused to testify.
Adam Schiff, the Democratic chair of the intelligence committee, said in his opening remarks that Congress would decide “in the coming days” whether Mr Trump’s conduct was impeachable. If the House impeaches Mr Trump, the Senate would hold a trial to decide whether to remove the president.
Nancy Pelosi, the Democratic speaker of the House, said Democrats would not get bogged down trying to enforce subpoenas for further testimony and documents in the courts but said they would take more time if needed.
“We cannot be at the mercy of the courts,” she said. “We are moving at the pace that truth takes us, and when more evidence unfolds if that requires more time that’s when we’ll go.”
Ahead of Ms Hill’s testimony, Devin Nunes, the ranking Republican on the House intelligence committee, hit back at her prepared remarks, holding up a copy of the panel’s 2018 report on Russian interference in the 2016 US presidential election.
“It’s entirely possible for two countries to engage in election meddling at the same time,” he told her.
Ms Hill on Thursday also gave her account of a key White House meeting that sparked the concern of her former boss, John Bolton, who was national security adviser at the time.
At the July 10 meeting involving Mr Bolton, Mr Sondland and Mr Volker, a national security adviser to Mr Zelensky, had asked when the Ukrainian president might be able to have a meeting at the White House.
Though Mr Bolton tried to change the subject, Mr Sondland intervened and said a deal had been done: investigations in return for the meeting. Ms Hill testified she later learned the deal had been struck by Mick Mulvaney, the acting White House chief of staff.
Ms Hill said she saw Mr Bolton “stiffen” at Mr Sondland’s comments, and then quickly wrap up the meeting. He later instructed her to tell the top lawyer on the National Security Council, John Eisenberg, that he was “not part of whatever drug deal Mulvaney and Sondland are cooking up,” she told the committee.
Mr Holmes recounted his own interactions with Mr Sondland, including a phone call the ambassador had with Mr Trump at a restaurant in Kyiv, a day after the infamous phone call in which the president asked Mr Zelensky to investigate the Bidens.
He said he had overheard the conversation because Mr Trump’s voice was “loud and recognisable”, allowing him to hear the president’s words even though the phone was not on speakerphone.
Mr Sondland told the president that Mr Zelensky “loves your ass”, Mr Holmes recalled. The aide said he heard the president ask whether the Ukrainian president would do the “investigation” and that Mr Sondland replied “he’s gonna do it”.
Immediately afterward, Mr Holmes said Mr Sondland told him the president did not “give a s — t about Ukraine” and only cared about “big stuff” like the “Biden investigation”.
Mr Sondland said Wednesday he did not recall mentioning the Bidens, but otherwise did not dispute Mr Holmes’ testimony.