The potentially historic, if hotly disputed, testimony from U.S. Ambassador to the European Union Gordon Sondland is the most damaging yet for Trump in Congress’s intensifying inquiry into whether the president should be impeached.

More forcefully than he has before, Sondland declared that the Trump administration would not give Ukraine’s newly elected president, Volodymyr Zelensky, a chance to visit the White House — unless Zelensky agreed to announce investigations that could help the president politically.

“I know that members of this committee frequently frame these complicated issues in the form of a simple question: Was there a ‘quid pro quo’?” Sondland said. “. . . With regard to the requested White House call and the White House meeting, the answer is yes.”

Sondland came to Capitol Hill as perhaps the most anticipated witness of the Democrats’ inquiry — a longtime Republican donor and Trump loyalist whose shifting accounts made it unclear which side of the political aisle his testimony might benefit more. He said after the hearing that he intended to stay in his post. But nearly from the moment his testimony began, it was clear he was ready to cast aspersions not just on the president, but also on the highest-ranking officials in his government.

Sondland acknowledged that he and others were the ones pushing Ukrainians to announce investigations, but asserted they had merely “followed the president’s orders,” communicated through Trump’s personal lawyer Rudolph W. Giuliani. Sondland testified that top-level officials — including Pence, acting White House chief of staff Mick Mulvaney and Secretary of State Mike Pompeo — were made aware at various points of what was happening, and he provided emails to back up his assertions.

“Everyone,” Sondland testified, “was in the loop.”

Sondland had previously faced significant questions about his credibility, and even as it was ongoing, his testimony Wednesday drew disputes from some of those he implicated. Republicans also seized on his lack of direct knowledge for some assertions, noting he admitted he never “personally” discussed with Trump the idea that either military aid or a White House meeting was preconditioned on Ukraine conducting investigations.

In his defense, Trump zeroed in on one favorable, but misleading, part of how Sondland described a September phone call between the two.

Sondland at the time had just received a text message from the acting U.S. ambassador to Ukraine, worried that the White House was conditioning nearly $400 million in aid on the country committing to the investigations targeting Democrats. Sondland later replied in a text message — which became an early piece of evidence submitted in the impeachment inquiry, and a rallying cry for Trump’s defenders — that the president wanted “no quid pro quo’s of any kind.”

Sondland testified last month, and again on Wednesday, that the phrase came directly from Trump in a phone call before he sent the text. Sondland said he had no knowledge of whether the president was telling him the truth at the time, at least with regard to the funding portion of the quid pro quo. Sondland said he had already been involved for weeks in bartering a White House visit for Ukraine as a condition of announcing the investigations.

Trump, nonetheless, focused on the part of the testimony where Sondland said he got the phrase from Trump.

“I want nothing. I want nothing. I want no quid pro quo. Tell Zelensky to do the right thing,” Sondland recalled Trump saying in the phone call.

Trump carried with him handwritten notes of Sondland’s words as he spoke to reporters outside the White House. He later tweeted them, adding: “This Witch Hunt must end NOW. So bad for our Country!”

Sondland testified Wednesday that he wished he’d typed the text differently back in September, using quotation marks to make clear the no quid pro quo phrase had come from Trump. It was “not artfully written,” he said.

Democrats said Sondland’s testimony revealed the extent of the Ukraine pressure campaign, noting in particular the allegations against senior administration officials.

“We now can see the veneer has been torn away,” House Intelligence Committee Chairman Adam B. Schiff (D-Calif.) told reporters during a break in the testimony, arguing that the situation as described by Sondland “goes right to the heart of the issue of bribery, as well as other potential high crimes or misdemeanors.”

In an attempt to bolster that allegation later in the evening, Democrats sought testimony from Laura Cooper, the deputy assistant secretary of defense for Russia and Ukraine, and David Hale, the undersecretary of state for political affairs — who focused particularly on the withheld military aid.

Cooper notably testified that a member of her staff fielded a question on July 25 from a Ukrainian embassy contact about what was happening with the security assistance — a new timeline that raises significant questions for the administration.

That morning, Trump had personally pressed Zelensky on a phone call for an investigation of former vice president Joe Biden — although security assistance was not explicitly tied to the request, according to a rough transcript of the call released by the administration.

Conservatives have asserted that Trump could not have been using a hold on assistance to extort an investigation from Ukraine, because the Ukrainians were not aware of it until much later. Cooper’s account could cast doubt on that — though members of Zelensky’s inner circle have said they didn’t know the aid was withheld until much later. The White House pushed back, saying: “Simply discussing the aid in no way means they knew it was being withheld.”

Sondland conceded it was his “guess” that the administration was tying military aid to Ukrainian investigations — an inference based on his real-time observation that the aid was being held back as Giuliani pressed officials in Kyiv to make an announcement.

“Is the only logical conclusion to you that — given all of these factors — that the aid was also a part of this quid pro quo?” Daniel Goldman, a lawyer for House Intelligence Committee Democrats, asked Sondland.

“Yep,” Sondland responded.

Sondland acknowledged later that his assessment was not informed directly by knowledgeable officials. He also conceded he and Trump had never directly discussed preconditions for the Ukrainians to get a White House meeting. But on that point — unlike the military aid — Sondland claimed Giuliani drew a connection.

“When the president says talk to my personal attorney — and then Mr. Giuliani as his personal attorney makes certain requests or demands — we assume it’s coming from the president,” Sondland said.

Giuliani wrote on Twitter that Sondland was “speculating based on VERY little contact.”

Although Sondland had testified previously behind closed doors, significant questions had been raised about his account, to which he appended some corrections. He professed throughout his testimony to have an imperfect memory of events, though he asserted that was in part because the White House and State Department had prevented him from reviewing relevant materials that might refresh his recollection.

“It would have been easier to testify if I had a totality of the record,” he said. The State Department claimed later he had full access to his records.

Trump had once praised Sondland, who gave $1 million to the Trump’s presidential inaugural committee, as “a really good man and great American.” But when White House lawyers had pressed in recent days to learn what he might say, Sondland’s lawyers rebuffed them, people familiar with the matter said, speaking on the condition of anonymity because of the impeachment inquiry’s extreme sensitivity. Trump has more recently sought to distance himself from Sondland, saying the diplomat was not someone he knew well.

Sondland said that he, Energy Secretary Rick Perry and Kurt Volker, at the time a special envoy to Ukraine, worked with Giuliani in pressing Ukraine “at the express direction of the president of the United States” — even though they were reluctant to do so.

At least initially, though, Sondland said he did not believe he was engaging in anything “improper” — in part because he claimed he did not understand that Trump wanted an investigation of Biden. Other witnesses have disputed that account.

Sondland said he did not listen in on the president’s July 25 call in which Trump specifically mentioned Biden and was not made aware of it in real time.

That call, and a subsequent whistleblower complaint about it, helped spark Democrats’ impeachment inquiry. The FBI recently has sought to interview the whistleblower, although no date has been set and it is unclear if one ever will, people familiar with the matter said.

“That would have changed my entire calculus, if President Trump would have told me directly,” he said. Sondland noted several times that it would be wrong for a president to pressure a foreign leader to investigate a political opponent.

Sondland said that while he knew one of the probes Giuliani was pushing to have announced was of Burisma, a Ukrainian energy company that had employed Biden’s son on its board, he did not connect that to the Bidens themselves. The other probe, he said, had to do with a theory among some conservatives that Ukraine was involved in misinformation in the 2016 U.S. presidential election.

Sondland said Giuliani seemed more focused on getting Ukraine to publicly reveal the investigations, rather than actually carry them out, though he conceded official announcements would hold foreign officials to their word.

Sondland said his work pushing Ukraine was “no secret,” and Pompeo, Pence, Mulvaney and then-national security adviser John Bolton were among those made aware of it at various times, in various ways.

Pompeo, Sondland asserted, “was aware that a commitment to investigations was among the issues we were pursuing.”

To support his case, Sondland revealed an email showing that he asked Pompeo to help him orchestrate a face-to-face encounter between Trump and Zelensky, off to the side of a World War II commemoration ceremony that the two were scheduled to attend in Poland on Sept. 1.

“I would ask Zelensky to look him in the eye and tell him that once Ukraine’s new justice folks are in place mid-Sept, that Ze should be able to move forward publicly and with confidence on those issues of importance to Potus and to the US,” Sondland wrote in the Aug. 22 email, using an acronym for president of the United States. “Hopefully, that will break the logjam.”

“Should we block time in Warsaw for a short pull-aside for Potus to meet Zelensky?” Sondland asked.

“Yes,” Pompeo replied three minutes later.

Days later, Trump decided not to travel to Warsaw and to instead stay in the United States as Hurricane Dorian threatened Florida. Pence made the trip in place of Trump. Sondland claimed he informed the vice president before the meeting “that I had concerns that the delay in aid had become tied to the issue of investigations.”

Pence’s chief of staff, Marc Short, disputed that account, asserting that Pence “never had a conversation with Gordon Sondland about investigating the Bidens, Burisma, or the conditional release of financial aid to Ukraine based upon potential investigations.” Pence himself said: “I have no recollection of any discussion with Ambassador Sondland before that meeting.”

Ultimately, Sondland would use the meeting to have his own, impromptu meeting with Zelensky confidant Andriy Yermak, in which he told his foreign counterpart release of the aid “would likely not occur” until Ukraine took some kind of action on publicly committing to the investigations Trump sought.

“My belief was that if Ukraine did something to demonstrate a serious intention” to launch the investigations Trump wanted, “then the hold on military aid would be lifted,” Sondland testified.

State Department spokeswoman Morgan Ortagus said: “Gordon Sondland never told Secretary Pompeo that he believed the President was linking aid to investigations of political opponents. Any suggestion to the contrary is flat out false.”

While Trump and others focused narrowly on Sondland’s description of his call with the president, conservatives were clearly frustrated with the ambassador.

Rep. Scott Perry (R-Pa.) blamed Sondland for the Ukraine controversy, accusing him of listening to the word of Giuliani over the president and of offering shifting accounts.

“It’s obvious the guy’s not sure what the heck he thinks,” Perry said.

Indeed, Sondland’s account in his prepared remarks that there were conditions on the aid and that he relayed those to Ukrainian officials reversed some aspects of his closed-door testimony in the impeachment inquiry a month ago.

During more than seven hours of questioning on Oct. 17, both Republicans and Democrats repeatedly asked Sondland whether aid was part of the White House quid pro quo. Numerous times, he said he could not recall.

After his denials were contradicted in testimony later provided by William B. Taylor Jr., the acting U.S. ambassador to Ukraine, and Tim Morrison, the former top Russia and Europe adviser on the National Security Council, Sondland filed a supplemental statement, stating the testimony of Taylor and Morrison had “refreshed my recollection about conversations involving the suspension of U.S. aid.”

Sondland also for the first time on Wednesday acknowledged a colorful July 26 call with Trump, placed from a restaurant in Kyiv, that a different witness already had described to lawmakers.

That witness, David Holmes, a counselor in the U.S. Embassy in Ukraine, told lawmakers he overheard Trump ask if Sondland was “gonna do the investigation.” Holmes said Sondland told Trump, “President Zelensky loves your ass.”

Sondland testified Wednesday that he recalled the conversation only after hearing Holmes describe a different portion of it, in which he and Trump described rapper A$AP Rocky. He conceded that portions Holmes’s description were likely true.

“Sounds like something I would say,” Sondland said, drawing laughter from the audience. “That’s how President Trump and I communicate, a lot of four-letter words.”

Holmes is scheduled to testify Thursday, along with Fiona Hill, a former top Russia expert for the White House.

Devlin Barrett, Josh Dawsey, Mike DeBonis, Karoun Demirjian, Kayla Epstein, Rosalind S. Helderman, John Hudson, Colby Itkowitz, Greg Jaffe, Paul Kane, Isabelle Khurshudyan, Michael Kranish, Carol D. Leonnig, Ellen Nakashima, Felicia Sonmez, Paul Sonne, Elise Viebeck and John Wagner contributed to this report.