US envoy testifies that release of Ukraine aid was contingent on public declaration to investigate Bidens, 2016 election

And here's Ambassador Taylor's opening statement.

[In addition to regular diplomatic channels, t]here was an irregular, informal channel of U.S. policy-making with respect to Ukraine, one which included then-Special Envoy Kurt Volker, Ambassador Sondland, Secretary of Energy Rick Perry, and as I subsequently learned, Mr. Giuliani. I was clearly in the regular channel, but I was also in the irregular one to the extent that Ambassadors Volker and Sondland
included me in certain conversations. Although this irregular channel was well-connected in Washington, it operated mostly outside of official State Department channels. This irregular channel began when Ambassador Volker, Ambassador Sondland, Secretary Perry, and Senator Ron-Johnson briefed President Trump on May 23 upon their return from President Zelenskyy’s inauguration. The delegation returned to Washington enthusiastic about the new Ukrainian president and urged President Trump to meet with him early on to cement the U.S.-Ukraine relationship. But from what I understood, President Trump did not share their enthusiasm for a meeting with Mr. Zelenskyy.

[...]

By mid-July it was becoming clear to me that the meeting President Zelenskyy wanted was conditioned on the investigations of Burisma and alleged Ukrainian interference in the 2016 U.S. elections. It was also clear that this condition was driven by the irregular policy channel I had come to understand was guided by Mr. Giuliani.

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During [a September 1] phone call I had with Mr. Morrison [the National Security Council's Senior Director for European and Russian Affairs], he went on to describe a conversation Ambassador Sondland had with Mr. Yermak [the assistant to President Zelenskyy] at Warsaw. Ambassador Sondland told Mr. Yermak that the security assistance money would not come until President Zelenskyy committed to pursue the Burisma investigation. I was alarmed by what Mr. Morrison told me about the Sondland-Yermak conversation.

This was the first time I had heard that the security assistance—not just the White House meeting—was conditioned on the investigations.

Very concerned, on that same day I sent Ambassador Sondland a text message asking if “we [are] now saying that security assistance and [a] WH meeting are conditioned on investigations?” Ambassador Sondland responded asking me to call him, which I did. During that phone call, Ambassador Sondland told me that President Trump had told him that he wants President Zelenskyy to state publicly that Ukraine will investigate Burisma and alleged Ukrainian interference in the 2016 U.S. election.

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I had been making (and continue to make) this point [that bipartisan support for Ukraine in Washington was Ukraine’s most important strategic asset and that President Zelenskyy should not jeopardize that bipartisan support by getting drawn into U.S. domestic politics] to all of my Ukrainian official contacts. But the push to make President Zelenskyy publicly commit to investigations of Burisma and alleged interference in the 2016 election showed how the official foreign policy of the United States was undercut by the irregular efforts led by Mr. Giuliani.

[O]n September 7, I had a conversation with Mr. Morrison in which he described a phone conversation earlier that day between Ambassador Sondland and President Trump. Mr. Morrison said that he had a “sinking feeling” after learning about this conversation from Ambassador Sondland. According to Mr. Morrison, President Trump told Ambassador Sondland that he was not asking for a “quid pro quo.” But President Trump did insist that President Zelenskyy go to a microphone and say he is opening investigations of Biden and 2016 election interference, and that President Zelenskyy should want to do this himself. Mr. Morrison said that he told Ambassador Bolton and the NSC lawyers of this phone call between President Trump and Ambassador Sondland.

But honestly, this paragraph really has everything you need to know.

The following day, on September 8, Ambassador Sondland and I spoke on the phone. He said he had talked to President Trump as I had suggested a week earlier, but that President Trump was adamant that President Zelenskyy, himself, had to “clear things up and do it in public.” President Trump said it was not a “quid pro quo.” Ambassador Sondland said that he had talked to President Zelenskyy and Mr. Yermak and told them that, although this was not a quid pro quo, if President Zelenskyy did not “clear things up” in public, we would be at a “stalemate.” I understood a “stalemate” to mean that Ukraine would not receive the much-needed military assistance. Ambassador Sondland said that this conversation concluded with President Zelenskyy agreeing to make a public statement in an interview with CNN.