Except the Ukrainians did know. The Times reported that “the Ukrainian government was aware of the freeze during most of the period in August when Mr. Trump’s personal lawyer Rudolph Giuliani and two American diplomats were pressing President Volodymyr Zelensky of Ukraine to make a public commitment to the investigations.”

This week, Gordon Sondland, ambassador to the European Union, testified that he explicitly told a top Ukrainian official that release of the aid was contingent on a public announcement of an investigation.

It’s all just hearsay. And the whistle-blower is a partisan Democrat.

Not just hearsay, but “triple hearsay.” This argument first appeared in October, as the outlines of the whistle-blower’s complaint came into focus. “Today was just more triple hearsay and selective leaks from the Democrats’ politically motivated, closed-door, secretive hearings,” said the White House Press secretary, Stephanie Grisham.

What about the anonymous whistle-blower? The president’s allies and conservative media outlets have been speculating about the person’s identity and motivations. But the truth is that the whistle-blower could have been Joe Biden himself at this point. What matters isn’t the motivation but the substance of the complaint. Virtually every element has been corroborated by multiple people.

It was a quid pro quo. But so what? This happens all the time.

“Did he also mention to me in passing the corruption related to the D.N.C. server?” Mick Mulvaney, the acting White House chief of staff, offered this during an October news conference. “Absolutely. No question about that,” he said. “That’s why we held up the money.”

For good measure, he added, “Get over it.”

To their credit, not even Mr. Trump’s most steadfast allies have signed on to this particular defense, at least not yet. Mr. Mulvaney, realizing the depth of the hole he had dug, later claimed he had not said what he said. Still, his claim did serve one important function, which was to pivot the administration’s basic case away from “no quid pro quo” to “yes, quid pro quo, but so what?”

It was a quid pro quo, but President Trump was only interested in rooting out corruption in Ukraine.