In late May, acting White House chief of staff Mick Mulvaney organized a meeting that stripped control of the country’s relationship with Ukraine from those who had the most expertise at the National Security Council and the State Department.

Instead, Mulvaney put an unlikely trio in charge of managing the U.S.-Ukraine account amid worrisome signs of a new priority, congressional officials said Tuesday: pressuring the fledgling government in Kiev to deliver material that would be politically valuable to President Trump.

The work of those “three amigos,” as they came to call themselves — diplomats Gordon Sondland and Kurt Volker, plus Energy Secretary Rick Perry — has come to light in recent days through newly disclosed text messages and the testimony of government witnesses appearing before an impeachment inquiry in Congress.

The Fact Checker unravels what happened when Trump tried to force an investigation into the false rumor about then-Vice President Joe Biden and Ukraine. (The Washington Post)

But Mulvaney’s connections to the administration’s troubled interactions with Ukraine are also beginning to surface. Mulvaney’s role in enlisting Sondland and the others to take over relations with Ukraine was revealed Tuesday in testimony by George Kent, the State Department’s Ukraine expert, according to Rep. Gerald E. Connolly (D-Va.), who participated in the closed-door hearing before the House Intelligence, Foreign Affairs and Oversight committees.

Mulvaney declined requests for comment. Some of his defenders have said he knew very little about the details of the trio’s efforts in Ukraine and was mainly orchestrating meetings for the president.

“I don’t remember any substantive conversation with Mick. I don’t remember him approving, disapproving, getting involved, having an interest,” said Rudolph W. Giuliani, who, as Trump’s personal lawyer, also served as the president’s emissary to Ukraine. “Mulvaney was not a big player in this. I dealt with Volker and Sondland.”

But current and former officials, speaking on the condition of anonymity to discuss internal matters, said Mulvaney contributed substantially to the unfolding political crisis, both through his connection to key events related to the attempt to pressure Kiev and through his general approach to the chief of staff job, which was driven by a perceived reluctance to displease the president.

U.S. officials said Mulvaney met frequently with Sondland and that details of their discussions were kept from then-National Security Adviser John Bolton and other officials who were raising internal concerns about the hidden Ukraine agenda.

Mulvaney also tolerated meetings between Trump and Giuliani at a time when Giuliani was brazenly declaring in interviews his intent to enlist Kiev in efforts to substantiate conspiracy theories about the 2016 election and revive seemingly dormant probes that could prove damaging to Democratic presidential candidate Joe Biden.

Perhaps most significantly, Mulvaney — at the direction of the president — placed a hold on nearly $400 million in aid to Ukraine in the weeks before Trump used a July 25 phone call to pressure Ukrainian President Volodymyr Zelensky to pursue Giuliani’s agenda. The impeachment probe was triggered in August by a whistleblower complaint submitted by a CIA employee to the U.S. intelligence community’s inspector general; the complaint focused in part on the July 25 call.

When some in the White House questioned the legality of blocking funds to Ukraine — funds approved by Congress to help fend off Russian attacks on its sovereignty — U.S. officials said Mulvaney told staff that he had determined that the money could be turned on and off with no legal consequence.

During his call with Zelensky, Trump emphasized how much aid Ukraine received from the United States, noting that he didn’t believe America’s largesse had been reciprocated. He then asked for “a favor, though,” pushing Zelensky to revive an investigation of an energy company, Burisma, that had paid Biden’s son Hunter to serve on its board.

Trump also prodded Zelensky to dig into a conspiracy theory that it was Ukraine — not Russia — that had interfered in the 2016 presidential election, and that hacked computer hardware from the Democratic National Committee had been smuggled to Ukraine to hide the evidence.

Sondland, Volker and Giuliani had laid the groundwork for that call over months of meetings with Ukrainian officials, texting one another the need to secure a commitment to produce what Sondland described as Trump’s “deliverable.”

That largely off-the-books effort could not have proceeded, current and former administration officials said, without Mulvaney facilitating meetings, halting the flow of aid and circumventing the national security bureaucracy.

In a measure of the internal tension and suspicion, Fiona Hill, who served as Trump’s top Russia adviser until leaving the administration in August , testified this week that Bolton urged her to alert White House lawyers to troubling developments related to Ukraine. She said Bolton had vowed that he would not be “part of whatever drug deal Sondland and Mulvaney are cooking up.”

U.S. officials said the friction between Mulvaney and Bolton led to a series of ruptures, including one on the day of the July 25 phone call. The White House has launched a formal internal review of the call and the circumstances around it, according to a senior administration official. The move was first reported by the New York Times.

Bolton, already troubled by the administration’s interactions with Ukraine, insisted that he alone handle the pre-call briefing with the president. But Sondland, who as U.S. ambassador to the European Union is based in Brussels, demanded that he also participate in the prep session.

Mulvaney backed Sondland, urging that he be allowed on the call, according to a White House official. When Bolton refused, Mulvaney appears to have again found a way to bypass the national security adviser. Bolton proceeded to brief the president solo, but then Sondland was patched through on a separate call.

In a July 26 interview on an English-language Ukrainian television program, Sondland said he “actually spoke with President Trump just a few minutes before he placed the call.”

Since he was thrust into the role of chief of staff early this year, officials said, Mulvaney has been more acquiescent to Trump than his predecessor, John Kelly, who sought to impose greater discipline in the White House and restrict access to the president.

Sondland “was talking to Mulvaney all the time,” said a former U.S. official familiar with their interactions. When confronted by Bolton or Hill, the official said, Sondland would rebuff them, saying he felt no obligation to coordinate with them because he had direct lines to Trump and Mulvaney.

“Mulvaney has really abdicated the most important duty of any White House chief of staff, and that’s to tell the president hard truths,” said Chris Whipple, author of “The Gatekeepers,” a book about previous White House chiefs of staff. “He really should have thrown his body in front of that phone call with Zelensky.”

One of Mulvaney’s top aides, Rob Blair, listened to the Trump-Zelensky call and briefed Mulvaney afterward, a White House official said. The official said that Mulvaney began inquiring more urgently about the call only weeks later, after the whistleblower report surfaced.

That complaint alleged that White House officials had taken the unusual step of moving a rough transcript of the Trump-Zelensky call into a highly classified database typically reserved for covert intelligence programs and operations.

Mulvaney asked John Eisenberg, the top lawyer for the National Security Council, about the decision to move the record of the phone call. Eisenberg replied that he had instructed NSC officials to restrict access to the rough transcript but did not specifically direct them to place it on the classified server — implying they had done so of their own volition, the official said.

A former South Carolina congressman who came to Washington as part of the 2010 tea party movement, Mulvaney was installed as acting chief of staff in January. His promotion followed the departure of an array of senior administration officials — including former defense secretary Jim Mattis — who seemed more inclined to challenge Trump’s decisions, especially on foreign policy.

“The fundamental issue . . . is that none of the president’s top advisers agree with his view of foreign policy. None of them,” said a former senior National Security Council official. “None of his principals share his views because they are so idiosyncratic.”

Mulvaney, by contrast, didn’t have strong opinions when it came to international affairs. He was more in sync with Trump, sharing the president’s “America First” view that the U.S. government should be doing far less abroad and that other countries should be doing far more.

Unlike Kelly, who often seemed to chafe at Trump’s impulsive decisions, officials said, Mulvaney’s primary goal often seemed to be pleasing the president.

Aaron C. Davis and Toluse Olorunnipa contributed to this report.

The Post has updated this story to make clear that Sondland says he spoke with President Trump shortly before the president’s July 25 call with Zelensky. A previous version of this story indicated otherwise based on information provided by a person familiar with Sondland’s planned testimony.