News photos of Ambassador William B. Taylor, Jr., leaving Capitol Hill on Tuesday evening showed him to be a white man with light-gray hair. He was wearing steel glasses and a dark suit. If you had to pick him out of a police lineup, about the only distinguishing feature that would help you are his thick eyebrows. But the chief diplomat at the U.S. Embassy in Kiev is no longer anonymous. With his testimony to House lawmakers, Taylor has made it a racing certainty that Democrats will bring impeachment charges against Donald Trump. Arguably, he has also removed the automatic presumption that Trump will survive an impeachment trial.

To be sure, impeachment charges have been likely ever since the House Intelligence Committee released a complaint from an anonymous intelligence whistle-blower, on September 26th, which alleged that the White House put a hold on military aid to Ukraine at the same time that Trump and his sidekick Rudy Giuliani were demanding that the recently elected President of Ukraine, Volodymyr Zelensky, launch a pair of investigations—one into Ukraine’s possible involvement in the 2016 U.S. Presidential campaign, the other into Burisma, the Ukrainian energy company that hired Hunter Biden. It was the whistle-blower’s complaint that prompted Nancy Pelosi, the Democratic Speaker of the House, to announce that an impeachment inquiry had officially begun, and to shift its focus from the purview of the Judiciary Committee to that of the Intelligence Committee.

As I remarked at the time, the whistle-blower’s complaint alleged a “flagrant abuse of Presidential power for personal gain (precisely the sort of behavior that James Madison and his colleagues were concerned about when they insisted upon including an impeachment clause in the U.S. Constitution),” but it didn’t provide conclusive proof that Trump tied the resumption of Ukrainian aid to his demand for investigations. From the whistle-blower’s position, he or she didn’t have sufficient access and information to nail down that detail.

Taylor did, though, and he took notes. On September 1st, he spoke by phone with Gordon Sondland, the Seattle hotel magnate and Trump donor who serves as the U.S. Ambassador to the European Union; Sondland had got caught up in Trump and Giuliani’s Ukraine caper, even though Ukraine isn’t in the E.U. “During that phone call,” Taylor said in his statement, “Ambassador Sondland told me that President Trump had told him that he wants President [Zelensky] to state publicly that Ukraine will investigate Burisma and alleged Ukrainian interference in the 2016 U.S. election. Ambassador Sondland also told me that he now recognized that he had made a mistake by earlier telling the Ukrainian officials to whom he spoke that a White House meeting with President [Zelensky] was dependent on a public announcement of these investigations—in fact, Ambassador Sondland said, ‘everything’ was dependent on such an announcement, including security assistance. He said that President Trump wanted President [Zelensky] ‘in a public box’ by making a public statement about ordering such investigations.”

On September 8th, Taylor and Sondland spoke again. Sondland “said he had talked to President Trump as I had suggested a week earlier, but that President Trump was adamant that President [Zelensky] himself had to ‘clear things up and do it in public.’ ” Taylor recalled Sondland saying that Trump told him “it was not a ‘quid pro quo.’ ” But, as “Ambassador Sondland tried to explain to me, President Trump is a businessman. When a businessman is about to sign a check to someone who owes him something . . . the businessman asks that person to pay up before signing the check.”

Perhaps Sondland will dispute Taylor’s version of the September 1st and September 8th phone calls, but how credible would that be? When Marie Yovanovitch, the former Ambassador to Kiev whom Trump fired, testified on Capitol Hill a couple of weeks ago, she set an example for other career officials, who are now coming forward to tell different versions of the same story and, by extension, to defend their values and vocations.

As he recounted in his opening statement, Taylor has served the United States for fifty years, “starting as a cadet at West Point, then as an infantry officer for six years, including with the 101st Airborne Division in Vietnam,” then at the Department of Energy, the U.S. Senate, and NATO. He then became a Foreign Service officer at the State Department, and served in Afghanistan, Iraq, Israel, and twice in Ukraine—as the U.S. Ambassador, from 2006 to 2009, and, from June of this year, when he replaced Yovanovitch, as the interim chargé d’affaires. When Mike Pompeo, the Secretary of State, asked Taylor to replace Yovanovitch, Taylor hesitated, because she “had been treated poorly, caught in a web of machinations both in Kyiv and in Washington.” Taylor spoke with Yovanovitch, who urged him to go for policy reasons and to boost the morale of people in the U.S. Embassy. He also spoke with an old mentor, “a respected former senior Republican official,” who told him, “if your country asks you to do something, you do it—if you can be effective.”

Taylor’s testimony on Tuesday was so effective that Trump had virtually no response to it after it leaked. All he could muster was a tweet quoting a Republican congressman who went on Fox News to claim that there couldn’t have been a quid pro quo because the Ukrainian government didn’t know that U.S. aid was being withheld. That crackpot theory was about as persuasive as the statement that Matthew Whitaker, the former interim Attorney General, made to Fox’s Laura Ingraham: “Abuse of power is not a crime.” On Wednesday, the Times reported that, as Giuliani and others urged Zelensky to investigate the Bidens, top officials in Ukraine were, in fact, well aware that the three hundred and ninety-one million dollars in military assistance was being held back by the White House.

Trump and his supporters are rattled, and for good reason. If this were an ordinary criminal trial, the lawyers for the defendant would be getting on the phone with the prosecutors and opening negotiations about a plea bargain. The Democrats aren’t open to offers, though. With witnesses like Taylor and Yovanovitch ready to be called on again in public hearings, and with even John Thune, the second-ranking Republican in the Senate, acknowledging that the picture presented so far “isn’t a good one,” Democrats are starting to sense they could be on to a winner.