At its core, President Trump’s defense in these impeachment proceedings is not a dispute over the facts of the case, the credibility of the witnesses or the motives of Democrats.

It is a bid to discredit the truth itself.

The Ukraine escapade began, in large part, because Trump pursued a conspiracy theory that Ukraine had interfered in the 2016 election to bring about his defeat, a false notion spread by Vladimir ­Putin and ultimately — with the help of Rudy Giuliani and others — embraced by the president himself.

But to defend Trump, a number of Republicans have concluded that they must establish that he had good reason to believe Ukraine was, in fact, out to get him. They must defend the Putin-planted conspiracy theory.

“Some government officials opposed President Trump’s approach to Ukraine but many had no idea what concerned him,” says Rep. Devin Nunes (Calif.), the ranking Republican on the House Intelligence Committee and the principal proponent of this view. “It was numerous indications of Ukrainian interference in the 2016 election to oppose his campaign and support Hillary Clinton. Once you know that, it’s easy to understand the president’s desire to get to the bottom of this.”

But on Thursday morning, that defense collided with a rock-solid obstacle: Fiona Hill, a Russia expert from the National Security Council who had a front-row seat to the administration’s shenanigans in Kyiv and who used her impeachment testimony to denounce the whackadoodle theory.

“Based on questions and statements I have heard, some of you on this committee appear to believe that Russia and its security services did not conduct a campaign against our country — and that perhaps, somehow, for some reason, Ukraine did,” she testified in the accent of her native northern England. “This is a fictional narrative that has been perpetrated and propagated by the Russian security services themselves.”

She continued her scolding, at length: “I refuse to be part of an effort to legitimize an alternative narrative that the Ukrainian government is a U.S. adversary, and that Ukraine — not Russia — attacked us in 2016.”

Nunes, who had read Hill’s written testimony, delivered a prebuttal before she delivered it. It’s not true, he said, that “some committee members deny that Russia meddled in the 2016 election.”

No? Exactly 71 seconds earlier, Nunes had referred to the matter as the “Russia hoax.”

The attempt to shift blame to Ukraine has been a daily refrain for Nunes. Democrats “turned a blind eye to Ukrainians meddling in our elections,” he said, ignoring “an election meddling scheme with Ukrainian officials on behalf of the Democratic National Committee and the Clinton campaign.”

It appears Nunes may have had a hand in shaping Trump’s view, too. Hill, during her deposition, said Kash Patel, a former Nunes staffer who joined the White House, apparently shared information with Trump about Ukraine — so much so that Trump seemed to think Patel was the NSC’s Ukraine director. Hill said “it alarmed everybody.”

After Politico reported on the deposition (the transcript has since been released), Patel on Monday filed a $25 million lawsuit against the news outlet. His lawyer is the same one who has represented Nunes in a variety of lawsuits against some 60 people and entities — including various journalists, news organizations and a Twitter user pretending to be Devin Nunes’s cow — that Nunes believes have done him wrong.

Nunes has been waging a broader campaign against the media, saying they “lurch from the Russia hoax to the Ukraine hoax at the direction of their puppet masters.”

Among Nunes’s pieces of evidence implicating Ukraine: an op-ed critical of Trump by a Ukrainian ambassador; a former DNC official who worked with Ukrainian officials “to dig up dirt on the Trump campaign”; and support by some Ukrainian officials for Hillary Clinton. Another allegation, offered by Trump in his now-infamous phone call, has Ukraine harboring a secret Democratic server.

Hill, during her testimony, dismissed the server fantasy. Though critical of Ukrainian officials who disparaged Trump, she explained that “many officials from many countries” did the same, and the Ukrainian detractors appeared to be individuals, unlike Russia’s top-down assault.

Nunes didn’t challenge Hill directly on Ukraine, instead taking a detour into Fusion GPS, the Steele dossier and other recurring elements of the fever dream he shares at each hearing. Apparently, he didn’t want to go toe to toe with her on what she called “politically driven falsehoods that so clearly advance Russian interests.”

“The impact of the successful 2016 Russian campaign remains evident today,” she said. “Our nation is being torn apart. Truth is questioned.”

And Devin Nunes fights, with all his might, for a fiction.

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