UNABLE TO answer the mounting evidence that President Trump abused his office to advance his reelection campaign, the White House is resorting to character assassination. Following reports of the congressional testimony Tuesday of William B. Taylor Jr., the acting ambassador to Ukraine, a statement attributed to press secretary Stephanie Grisham described “a coordinated smear campaign from far-left lawmakers and radical unelected bureaucrats waging war on the Constitution.” We’ll let House Democrats defend themselves. But the attempt to sully Mr. Taylor’s reputation, and that of other government servants who have testified in the Ukraine affair, is ludicrous — and vile.

For the record: Mr. Taylor has served his country with distinction for 50 years. After graduating from West Point, he was deployed for six years as an infantry officer, including with the 101st Airborne Division in Vietnam. Later he worked at NATO and as a State Department diplomat in Afghanistan, Iraq, Israel and Ukraine, where he was first appointed ambassador by George W. Bush.

In his testimony Tuesday, Mr. Taylor recounted that, after being asked to return to Kyiv earlier this year by Secretary of State Mike Pompeo, he approached a former senior Republican official for advice. He said “the mentor counseled: ‘If your country asks you to do something, you do it — if you can be effective.’ ” Despite the strong opposition of his wife, the 72-year-old Mr. Taylor accepted the assignment.

We feel confident that it was in that same spirit that Mr. Taylor agreed to testify about Mr. Trump’s extortion of the Ukrainian government. He, and former ambassador Marie Yovanovitch, and Deputy Assistant Secretary of State George Kent, and former Pompeo adviser Michael McKinley, and former National Security Council aide Fiona Hill, are the opposite of “radicals.” They are conservatives in the best sense — patriots who tried, and are still trying, to defend the country’s interests and values from a radically reckless and corrupt president. They spoke in spite of the administration’s attempts to silence them and at the risk of losing jobs or otherwise becoming targets of retaliation.

Two others who testified, Kurt Volker and Gordon Sondland, are Republicans appointed to their posts by Mr. Trump. By Mr. Taylor’s account, Mr. Sondland, who donated $1 million to Mr. Trump’s inaugural committee, did not disclose to Congress all he did to advance Mr. Trump’s attempt to pressure Ukrainian President Volodymyr Zelensky into announcing investigations of Joe Biden and the Democratic National Committee. But even Mr. Sondland spoke openly of his unease over the hijacking of policy toward Ukraine by Mr. Trump’s personal lawyer, Rudolph W. Giuliani.

The accounts these men and women have provided establish beyond any reasonable doubt that Mr. Trump conditioned a White House meeting that Mr. Zelensky badly wanted on his commitment to investigations that would advance Mr. Trump’s personal political interests — and Mr. Taylor offered considerable evidence that Mr. Trump froze U.S. military aid to Ukraine for the same reason. That the testimony came behind closed doors is a drawback; though it might be necessary in this investigative phase, House leaders should arrange for the witnesses to tell their stories in public as the impeachment process moves forward.

Americans who see and hear Mr. Taylor, Ms. Yovanovitch and the others are likely to perceive them for what they are: honest and courageous public servants. Ms. Grisham, who in nearly four months on the job has yet to hold a public news conference, will be remembered — if she is remembered at all — as one of the political bullies who tried and failed to discredit them.

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