There is one primary political question surrounding President Trump’s interactions with Ukrainian President Volodymyr Zelensky: Was it appropriate for Trump to have asked Zelensky to launch an investigation into former vice president Joe Biden, a possible 2020 opponent of Trump’s? This is a legal question, too, of course, given that soliciting foreign assistance for a campaign is illegal. But it’s the political issue posed by Trump’s admitted request of Zelensky that’s the more urgent risk for the president.

Surrounding that question is another one: How, if at all, did Trump try to pressure Zelensky into doing what he wanted? As America became aware of the existence of a complaint about Trump’s actions filed by a whistleblower within the intelligence community, there was speculation that an unexplained halt on military aid to Ukraine was linked to Trump’s requests of the Ukrainian president. Over time, we learned that Trump had another carrot: a White House meeting with a newly elected leader hoping to establish his credibility.

The timeline of events surrounding Trump’s interactions with Zelensky and his focus on Ukraine has grown increasingly lengthy, particularly as more current and former administration officials offer testimony to the House committee leading the impeachment inquiry. The density of those events can obscure the above question. With that in mind, we’ve created a visual timeline of how and when there are suggestions that Trump and his team (including outside attorney Rudolph W. Giuliani) held something Zelensky wanted — the quids, if you will — and used them to try to extract things — quos — from him.

What were those things?

The possible quids
The possible quos
A meeting with Trump. Zelensky clearly hoped to be able to visit Trump at the White House. Before that meeting, Trump’s team debated setting up a phone call.
Investigations into Biden and 2016 interference. The former included Biden’s son Hunter Biden. The latter (inexplicably) included a look at the hacking of the Democratic Party in 2016.
Military and economic aid. This aid was originally reported to Congress in late February.
A public statement about the launch of investigations. For a brief period this summer, this was discussed.
Work with Russia and President Vladimir Putin. On multiple occasions, Trump encouraged Zelensky to work with Russia.

Many of the points of overlap here are open to subjective interpretation. To facilitate that interpretation, we created the graphic below. Included items are described below.

The initial context that’s important to recognize is that Giuliani had been agitating for months to launch a probe into the Bidens and, simultaneously, attacking then-U.S. Ambassador to Ukraine Marie Yovanovitch as insufficiently loyal to Trump. (Yovanovitch testified this week that she believed Giuliani was trying to protect his financial interests in the country.) Shortly after Zelensky won the presidency in April, she was recalled to the United States. A diplomat named Bill Taylor stepped in to replace her on an acting basis. (The names of key figures have been highlighted.)

According to The Washington Post’s reporting, at some point in May, Trump told his central Ukraine team — Energy Secretary Rick Perry, special envoy to Ukraine Kurt Volker and E.U. Ambassador Gordon Sondland — that a possible face-to-face meeting with Zelensky would need to be cleared by Giuliani. On May 14, Trump told Vice President Pence not to attend Zelensky’s inauguration later that month, according to the whistleblower. At about that same time, the whistleblower was told that a possible Trump-Zelensky meeting was dependent on Zelensky “playing ball” on investigations.

That would be an explicit quid pro quo: Meeting for investigations. Because it’s secondhand through the whistleblower, it’s indicated on the graphic with a dashed line and in the text is highlighted in orange instead of yellow.

In May and June, aid to Ukraine was on track. On June 18, the Defense Department publicly announced the imminent release of aid.

Three days later, Giuliani criticized Zelensky on Twitter for not launching investigations into the campaign and Biden.

In early July, there was a meeting at the White House involving then-National Security Adviser John Bolton, Perry, Sondland, Volker and then-Russia adviser Fiona Hill. According to the New York Times, Hill testified this week that, during that meeting, Sondland said a Trump-Zelensky meeting would be predicated on his launching the desired investigations. That requirement, he reportedly said, came from acting White House chief of staff Mick Mulvaney. Bolton reportedly told Hill to report the comments to White House lawyers.

A bit over a week later, aid to Ukraine was halted. The next day, July 19, Volker had breakfast with Giuliani. He reportedly testified he didn’t then connect the stopping of aid to the desired investigations. After their meeting, Volker connected Giuliani with Andrey Yermak, an adviser to Zelensky.

That afternoon, Sondland texted Volker to tell him it “looks like Potus call tomorrow” — apparently meaning a planned call between Trump and Zelensky. “I [spoke] directly to Zelensky and gave him a full briefing,” Sondland added.

Volker told Sondland about the Giuliani breakfast, which “must have helped.”

“Most impt,” he added, “is for Zelensky to say that he will help investigation — and address any specific personnel issues — if there are any."

Trump and Zelensky actually spoke July 25. Before the call, Sondland and Trump spoke. Volker sent a text message to Yermak: “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.”

During the call itself, Zelensky repeatedly asked for a meeting. He also mentioned soon wanting to buy Javelin missiles, aid included in the package announced in June by the Defense Department. Trump replied to the latter comment by saying that he needed a favor: that Ukraine look into a convoluted theory about a Ukrainian link to the hacking of the Democratic National Committee’s network in 2016. He encouraged Zelensky to work with Giuliani and Attorney General William P. Barr, who in May had launched an investigation into the origins of the probe into possible collusion between Trump’s 2016 campaign and Russia’s interference effort that year. Trump agreed to meeting Zelensky only after the Ukrainian president agreed to investigate the Bidens.

After the call, Yermak sent a list of proposed dates for Zelensky to visit.

On July 31, the whistleblower raised concerns about Trump’s call to the CIA’s general counsel, according to the Times. The counsel raised the issues with the same White House lawyer whom Hill had contacted after the July 10 meeting.

On Aug. 2, Yermak and Giuliani met in Madrid. The day after, Zelensky announced publicly he would be traveling to the United States.

But it wasn’t that easy. Asked on Aug. 9 by a foreign reporter whether Zelensky was coming to the United States, Trump suggested indirectly that a visit was linked to Zelensky working with Russian President Vladimir Putin.

“I think he’s going to make a deal with President Putin, and he will be invited to the White House,” Trump said. “And we look forward to seeing him. He’s already been invited to the White House, and he wants to come. And I think he will. He’s a very reasonable guy. He wants to see peace in Ukraine. And I think he will be coming very soon, actually.”

That same day, Volker and Sondland were exchanging text messages about another predicate for a meeting: a statement from Zelensky about new probes into Biden and 2016 interference.

Hill’s replacement, Tim Morrison, was “ready to get dates as soon as Yermak confirms,” Sondland told Volker. Asked how he’d persuaded Morrison, Sondland replied: “Not sure i did. I think potus really wants the deliverable.” That deliverable? Apparently the investigations which, it seems, Giuliani and Yermak had already discussed.

“To avoid [misunderstandings],” Sondland wrote to Volker, “might be helpful to ask Andrey [Yermak] for a draft statement (embargoed) so that we can see exactly what they propose to cover.”

Volker texted Giuliani the same day: “Had a good chat with Yermak last night. He was pleased with your phone call. Mentioned [Zelensky] making a statement. Can we all get on the phone to make sure I advise [Zelensky] correctly as to what he should be saying? Want to make sure we get this done right."

On Aug. 10, Yermak texted Volker to suggest reversing the order: Meeting first, then a statement or interview about new probes. On Aug. 13 and Aug. 17, Volker and Sondland discussed the possible statement. It included references to the Biden probe. If released, it would probably have not had any fingerprints from U.S. officials.

It wasn’t released. On. Aug. 28, Politico reported that aid to Ukraine had been blocked. The next day, Yermak texted Volker to discuss it. On Aug. 30, Trump canceled his planned trip to Poland where he was scheduled to meet with Zelensky.

That same day, Sondland spoke with Sen. Ron Johnson (R-Wis.) before the senator traveled to see Zelensky. According to Johnson, Sondland told him that Zelensky needed a prosecutor who could “get to the bottom of what happened in 2016 — if President Trump has that confidence, then he’ll release the military spending.” That made Johnson “wince,” he later told reporters.

The next day, Aug. 31, Johnson asked Trump whether he was withholding aid to pressure Ukraine to launch investigations. He wasn’t, Trump said — but then told Johnson that the aid was being withheld because of alleged corruption centered on the 2016 campaign.

On Sept. 1, Pence met with Zelensky. He later told reporters that aid was being withheld out of concerns about corruption.

“To invest additional taxpayer [money] in Ukraine,” Pence said about the meeting, “the President wants to be assured that those resources are truly making their way to the kind of investments that will contribute to security and stability in Ukraine.”

That same day, acting ambassador Taylor asked Sondland via text message if a meeting or aid were specifically conditioned on new investigations. Sondland told him to call.

A week later, Taylor, Sondland and Volker were still discussing a possible statement or interview announcing those investigations. Taylor expressed his concern: that the interview would happen but that the aid would still be withheld. This was his “nightmare.”

He reiterated that fear the next day, Sept. 9.

“As I said on the phone,” Taylor said to Sondland over text, “I think it’s crazy to withhold security assistance for help with a political campaign.”

Sondland replied five hours later, after speaking with Trump.

“Bill, I believe you are incorrect about President Trump’s intentions,” he replied to Taylor. “The President has been crystal clear no quid pro quo’s of any kind. The President is trying to evaluate whether Ukraine is truly going to adopt the transparency and reforms President Zelensky promised during his campaign[.] I suggest we stop the back and forth by text[.]”

The Post reported this weekend that the quid-pro-quo denial came from Trump, not from Sondland’s own assessments.

On Sept. 11, the aid was released, a day after Bolton left the White House. Two weeks later, Trump and Zelensky met for the first time, with Trump seizing upon Zelensky’s denial that he’d been pressured. He also reiterated his hope the Ukrainian president would work with Putin.

On Oct. 3, the State Department approved the sale of Javelin antitank missiles to Ukraine. Two days before that, Zelensky had announced his support for a compromise aimed at ending Ukraine’s conflict with Russia, a compromise that Russia quickly embraced.

Aaron Blake contributed to this report.