On Tuesday, nearly seven hours into the marathon third day of public impeachment hearings, Kurt Volker tried to explain to the House Intelligence Committee what it was like to carry out the nearly impossible task of wrangling U.S. policy toward Ukraine during the Presidency of Donald Trump. Volker, a veteran Republican diplomat who had been serving, since 2017, as Trump’s Special Representative to Ukraine, said that he realized last spring that he had a “problem,” and that it was Trump himself.

When Volker took the job, he testified, “I believed I could steer U.S. policy in the right direction,” an ambitious statement given that Trump had already been publicly skeptical of Ukraine and supportive of its adversary Russia. Still, Volker insisted that he thought he could maintain the long-standing U.S. policy of supporting Ukraine, a bipartisan priority ever since Russia illegally annexed Ukraine’s Crimean Peninsula, in 2014, and launched a proxy civil war in the country’s east. “If a problem arose, I knew that it was my job to try to fix it,” Volker said. In May, he learned that there was, in fact, a “significant problem”: the attitude of the President toward Ukraine. Trump, as Volker heard firsthand in an Oval Office meeting that month, believed that Ukraine was corrupt, “out to get” him, and harbored an animus going back to the 2016 election; he even embraced a discredited conspiracy theory that Ukraine, not Russia, had intervened in the U.S Presidential race. As a result, Trump was deeply skeptical toward the Administration’s own policy of supporting Ukraine and had no desire to meet with the country’s reformist new President, Volodymyr Zelensky. Volker believed that Trump was being fed misinformation about Ukraine by his private lawyer, Rudy Giuliani. “I found myself faced with a choice: to be aware of a problem and to ignore it or to accept that it was my responsibility to try to fix it,” Volker testified. “I tried to fix it.”

To say that he failed would, of course, be an understatement. Had Volker succeeded, there would not be an impeachment proceeding against Trump in the House of Representatives. Instead, just a few months after Volker tried to fix the problem, he was under oath on Capitol Hill, testifying, on Tuesday, along with three current and former White House officials. (“Impeachapalooza 2019,” as the Republican Chris Stewart called it.) All three of the witnesses who testified with Volker had listened in on Trump’s now infamous July 25th phone call with Zelensky, and in their testimony they recounted varying degrees of concern as they heard Trump demand that Zelensky do him the “favor” of investigating his political rival, the former Vice-President Joe Biden, and Ukraine’s role in the 2016 election. The witnesses called Trump’s actions “improper,” “inappropriate,” and “unusual,” and said that they potentially undermine the bipartisan American policy of supporting Ukraine.

The testimony on Tuesday morning of Lieutenant Colonel Alexander Vindman, who is currently serving as the National Security Council’s Ukraine expert, was particularly pointed. Wearing his Army dress blues and a chest full of decorations, Vindman delivered a devastating critique of his Commander-in-Chief. “I couldn’t believe what I was hearing,” Vindman said of listening to Trump’s July 25th phone call with Zelensky. “It is improper for the President of the United States to demand a foreign government investigate a U.S. citizen and political opponent,” Vindman said. When he heard Trump press Zelensky to investigate Biden, he believed that it was a “political play,” one with unmistakable implications for the Ukrainians, and that it would “undoubtedly result in Ukraine losing bipartisan support, undermine U.S. national security, and advance Russia’s strategic objectives in the region.” He went to the National Security Council’s lawyer after the call to report his concerns.

It was a remarkable moment, followed soon after by Vindman denouncing the “reprehensible” attacks by Trump and his supporters against himself and other witnesses from inside America’s nonpartisan national-security bureaucracy who have come forward to testify. Speaking truth to power as Vindman did—the lieutenant colonel publicly challenged the President of the United States while still serving on his staff—would never have been possible in the Soviet Union, where Vindman was born, or the Russia of today. Such public defiance of a leader would “surely cost me my life,” Vindman said. He was right: it never could have happened in Russia. It still seems unbelievable that it is happening in America.

If Tuesday morning offered the unprecedented spectacle of a uniformed officer taking on the President while still working in his White House, Volker’s testimony on Tuesday afternoon marked a moment in its own way, putting an end, hopefully once and for all, to the fallacy that anyone can manage, contain, steer, or constrain President Trump from pursuing even a misbegotten or highly politically perilous course. Volker is not the first but the latest to discover this fact, and with the catastrophic consequence of Presidential impeachment as the result.

The myth of the “adults in the room” has persisted since the beginning of the Administration, but it has never been accurate. There is no managing Donald Trump, no way to preserve one’s integrity while doing what is necessary to remain powerful in his orbit. Look at what happened to Rex Tillerson and Jim Mattis and John Kelly. Trump is a government of one. He himself has said so repeatedly. Early in his Administration, under criticism for leaving key posts open at the State Department, Trump said that, when it comes to foreign policy, “I am the only one that matters.” At the time, less than a year into his Presidency, perhaps that could have been dismissed as hyperbole. Certainly, it would have been surprising to hear members of Congress publicly agreeing that the entire rest of the government—themselves and their own branch included—was irrelevant. Yet that is more or less where the impeachment process has ended up.

Several of the witnesses in the impeachment inquiry found that out, to their dismay. Volker is perhaps the clearest example of this. Volker thought that he could handle the problem of Trump’s attitude toward Ukraine by engaging with the source of the “negative information flow”—Giuliani. Others in the Administration considered this folly and warned him that it was not feasible to “thread the needle,” as Volker termed it in his testimony. Yet he tried, awkwardly insisting that he had no idea that Trump actually wanted Zelensky to investigate Biden, as opposed to more generic “corruption” in Ukraine. Volker said that he had been out of the loop on the key conversations that would have revealed that motive. When he met Giuliani at the Trump International Hotel in Washington for breakfast, in July, Volker acknowledged that Giuliani did bring up Biden and that Volker tried to talk him out of it. It did not work.

Fiona Hill, the former National Security Council senior director for Russia and Ukraine, who will appear publicly on Thursday, said in her private deposition to investigators that both she and John Bolton, the national-security adviser at the time, told Volker directly and unambiguously not to talk with Giuliani. “We did say to him that we did not think it was a good idea for him to be talking to Rudy Giuliani,” Hill said. Volker’s response to her was instructive. He said that he could “reason with him and … manage this,” Hill recalled. “Well, we did not think this was manageable.”