WASHINGTON, DC - NOVEMBER 04: U.S. President Donald Trump talks to journalists while departing the White House November 04, 2019 in Washington, DC. Trump is traveling to Kentucky for a 'Keep America Great' campaign rally in Lexington, Kentucky. (Photo by Chip Somodevilla/Getty Images)
PHOTO: Chip Somodevilla/Getty Images
WASHINGTON, DC - NOVEMBER 04: U.S. President Donald Trump talks to journalists while departing the White House November 04, 2019 in Washington, DC. Trump is traveling to Kentucky for a 'Keep America Great' campaign rally in Lexington, Kentucky. (Photo by Chip Somodevilla/Getty Images)
Now playing
07:38
Trump ally changes testimony and admits quid pro quo
Now playing
01:21
Lawmaker fires back at Tucker Carlson's QAnon spin
Sen. Lisa Murkowski (R-AK) asks a question at a hearing of the Senate Health, Education, Labor and Pensions Committee on September 23, 2020 in Washington, DC.
PHOTO: Alex Edelman/Pool/Getty Images
Sen. Lisa Murkowski (R-AK) asks a question at a hearing of the Senate Health, Education, Labor and Pensions Committee on September 23, 2020 in Washington, DC.
Now playing
01:40
Trump plans to campaign against Sen. Murkowski in 2022
Biden 03062021
PHOTO: CNN
Biden 03062021
Now playing
02:28
'Help is on the way': Biden speaks after Senate passes relief plan
Now playing
03:04
Schumer: Nobody said it would be easy, but it is done
01 senate stimulus bill 210306
PHOTO: Senate TV
01 senate stimulus bill 210306
Now playing
01:47
Senate passes Biden's $1.9 trillion Covid-19 relief bill
WASHINGTON, DC - MARCH 05: Sen. John Cornyn (R) (R-TX) talks with Sen. Joe Manchin (D-WV) while walking to the U.S. Senate chamber for a vote March 05, 2021 in Washington, DC. The Senate continues to debate the latest COVID-19 relief bill.  (Photo by Win McNamee/Getty Images)
PHOTO: Win McNamee/Getty Images
WASHINGTON, DC - MARCH 05: Sen. John Cornyn (R) (R-TX) talks with Sen. Joe Manchin (D-WV) while walking to the U.S. Senate chamber for a vote March 05, 2021 in Washington, DC. The Senate continues to debate the latest COVID-19 relief bill. (Photo by Win McNamee/Getty Images)
Now playing
02:54
Axelrod breaks down Manchin's surprising move
sinema
PHOTO: CNN
sinema
Now playing
01:50
Senator's move has many on the internet outraged
PHOTO: FBI
Now playing
02:58
Trump State Department official charged in Capitol riot
WASHINGTON, DC - JANUARY 06: U.S. Sen. Paul Gosar (R-AZ) speaks on the floor of the House Chamber during a joint session of congress on January 06, 2021 in Washington, DC. Congress held a joint session today to ratify President-elect Joe Biden's 306-232 Electoral College win over President Donald Trump. A group of Republican senators said they would reject the Electoral College votes of several states unless Congress appointed a commission to audit the election results. (Photo by Drew Angerer/Getty Images)
PHOTO: Drew Angerer/Getty Images
WASHINGTON, DC - JANUARY 06: U.S. Sen. Paul Gosar (R-AZ) speaks on the floor of the House Chamber during a joint session of congress on January 06, 2021 in Washington, DC. Congress held a joint session today to ratify President-elect Joe Biden's 306-232 Electoral College win over President Donald Trump. A group of Republican senators said they would reject the Electoral College votes of several states unless Congress appointed a commission to audit the election results. (Photo by Drew Angerer/Getty Images)
Now playing
02:19
This is what Rep. Gosar was posting days before Capitol riot
John King Magic Wall 0305
PHOTO: CNN
John King Magic Wall 0305
Now playing
02:17
President Biden sending a team to the US-Mexico border
Senior Advisor to the President Jared Kushner  attends a press conference on September 4, 2020, in the Brady Briefing Room of the White House in Washington, DC. (Photo by Brendan Smialowski / AFP) (Photo by BRENDAN SMIALOWSKI/AFP via Getty Images)
PHOTO: BRENDAN SMIALOWSKI/AFP/AFP via Getty Images
Senior Advisor to the President Jared Kushner attends a press conference on September 4, 2020, in the Brady Briefing Room of the White House in Washington, DC. (Photo by Brendan Smialowski / AFP) (Photo by BRENDAN SMIALOWSKI/AFP via Getty Images)
Now playing
02:50
Jared Kushner disappears from Trump's inner circle
Rep john garamendi 0305
PHOTO: CNN
Rep john garamendi 0305
Now playing
02:33
Rep. Garamendi: Any lawmaker involved in Capitol riots ought to be thrown out of Congress
Protesters gather at Lincoln Park to demand the Emancipation Memorial be taken down on June 23, 2020 in Washington, DC.
PHOTO: Tasos Katopodis/Getty Images
Protesters gather at Lincoln Park to demand the Emancipation Memorial be taken down on June 23, 2020 in Washington, DC.
Now playing
03:01
Why some people want this Abraham Lincoln statue taken down
psaki
PHOTO: CNN
psaki
Now playing
00:56
Psaki fires back at Trump testing czar over vaccine claims
PHOTO: CNN
Now playing
03:04
Avlon: Pence's op-ed is 'way worse than Stockholm syndrome'
(CNN) —  

The impeachment inquiry has uncovered at least three examples of the quid pro quo between the Trump administration and Ukraine, where US military aid and a White House visit were used as leverage to secure an announcement that Ukraine was investigating President Donald Trump’s rivals, according to documents and testimony from key witnesses.

The question of whether there was a quid pro quo is at the heart of the impeachment inquiry.

Trump has been adamant that he did nothing wrong and tweeted at least 15 times since the inquiry began that there was no quid pro quo. Yet many Democrats have said from the start that they saw evidence of Trump attempting to trade US military assistance for political favors from Ukraine.

Legal analysts and experts on the impeachment process have said the investigation doesn’t actually need to find incontrovertible proof of a quid pro quo for the House to impeach Trump.

Nevertheless, after a month of interviews with senior Trump administration officials, lawmakers have unearthed at least three examples of the quid pro quo.

Here’s a complete breakdown:

The Volker text messages

Trump’s special envoy for Ukraine, Kurt Volker, told a senior Ukrainian official that the new Ukrainian President could secure a White House invite if he convinced Trump he would launch an investigation into potential Ukrainian meddling in the 2016 US presidential election.

This happened in a text message from Volker to Andrey Yermak, a senior aide to Ukrainian President Volodymyr Zelensky, a political newcomer who never held elected office before this year. It was sent shortly before an important call on July 25 between Trump and Zelensky.

Volker told Yermak in the text: “Good lunch – thanks. Heard from White House — assuming President Z convinces trump he will investigate / ‘get to the bottom of what happened’ in 2016, we will nail down date for visit to Washington. Good luck! See you tomorrow -kurt.”

Trump has never never fully accepted the fact that the Russian government interfered in the 2016 presidential election, hacking Democrats and leaking their emails to help him win. Instead, he has promoted unfounded conspiracy theories that Ukraine framed the Russians.

By asking Ukraine to explore these theories, the Trump administration was seeking information that could undermine the Russia investigation, which would be politically beneficial to Trump.

The Trump phone call

After Volker sent those texts, Trump got on the phone with Zelensky. During the July 25 conversation, Zelensky brought up US military assistance to Ukraine, which has been at the center of US policy since Russia and its proxies invaded Eastern Ukraine in 2014. Zelensky told Trump he was interested in buying additional anti-tank missiles that Ukraine could have in its arsenal.

“I would like you to do us a favor though,” Trump interjected, according to a rough White House transcript, “because our country has been through a lot and Ukraine knows a lot about it. I would like you to find out what happened with this whole situation with Ukraine, they say CrowdStrike … I guess you have one of your wealthy people … The server, they say Ukraine has it.”

This was the request for Ukraine to investigate the conspiracy theories about 2016. CrowdStrike is the California-based cybersecurity firm that helped the Democratic National Committee figure out that Russia was responsible for the hacking. During the call, Trump mentioned the unfounded theory that the DNC’s hacked servers were somehow hidden in Ukraine.

Later in their conversation, Trump asked Zelensky to work with his personal attorney Rudy Giuliani to investigate allegations of corruption by former Vice President Joe Biden and his son Hunter, who had a highly-paid position on the board of a Ukrainian energy company. Despite Trump and Giuliani’s claims there is no evidence of wrongdoing by the Bidens.

Trump never committed to the anti-tank missiles Zelensky requested during the call. Instead, Zelensky said he would look into the two politically charged matters that Trump brought up.

The Sondland pull-aside

As the summer progressed, a Trump-Zelensky meeting at the White House still had not been scheduled, and news reports revealed that there was an inexplicable holdup in US military and security aid for Ukraine – a $400 million package that was already approved by Congress.

Trump was meant to meet Zelensky at an event in Poland, but those plans fell through when Trump stayed home to deal with a hurricane. Zelensky met with Vice President Mike Pence instead. After that meeting, Zelensky’s aide Yermak had a conversation with US Ambassador to the European Union Gordon Sondland, a wealthy donor to Trump who handled Ukraine issues.

After first denying there was ever a quid pro quo offered to Ukraine, Sondland made a significant revision to his testimony this week in which he admitted that there was.

“I now recall speaking individually with Mr. Yermak, where I said that resumption of U.S. aid would likely not occur until Ukraine provided the public anti-corruption statement that we had been discussing for many weeks,” Sondland said in his revised testimony to House lawmakers.

The “anti-corruption statement” is an apparent euphemism for the public announcement that Trump hoped Zelensky would make, where Zelensky would say that Ukraine was investigating the allegations regarding Biden and his son, as well as potential Ukrainian meddling in 2016. A declaration like that would give Trump a major talking point to use against Biden on the trail.

Around the time of Sondland’s conversation with Yermak on September 1, other US officials got the sense that there was a quid pro quo linking US military aid to the Ukrainian investigations. This included Bill Taylor, the top US diplomat in Ukraine, as well as Lt. Col. Alexander Vindman, an expert on the White House’s National Security Council, according to their sworn testimony.