(CNN) In a July 25 phone call between President Donald Trump and Ukrainian President Volodymyr Zelensky, Trump asked his counterpart to look into debunked allegations of corruption by Joe Biden and his son, Hunter.

This is a fact. The Truth. How do we know? Because the White House released a rough transcript of the conversation last week in which Trump said this:

"There's a lot of talk about Biden's son, that Biden stopped the prosecution and a lot of people want to find out about that so whatever you can do with the Attorney General would be great. Biden went around bragging that he stopped the prosecution so if you can look into it... It sounds horrible to me."

See, it's right there. In the transcript the White House released itself.

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All of which makes this next fact absolutely mystifying and terrifying: In a new national Monmouth University poll just four in 10 self-identified Republicans believe that Trump mentioned Biden in his call with Zelensky.

Are. You. Kidding. Me.

It is right there in the transcript that the WHITE HOUSE released of the call!

Remember that we aren't talking here about whether Trump pressured Zelensky to look into the Bidens. He did, but there is a little bit of wiggle room there in that Trump didn't say "Unless you do this, I will withhold military aid from you." This poll question deals only with whether Trump actually mentioned Biden's name in the call. Which he 100% did!

How can so many Republicans say he didn't? Because Trump has conditioned them to not believe things that are, quite literally, right in front of their faces.

"Stick with us," Trump told a group of veterans last July . "Don't believe the crap you see from these people, the fake news. ... What you're seeing and what you're reading is not what's happening."

When you consider that the American President actually told people that "what you're seeing and what you're reading is not what's happening," this poll finding doesn't seem so unbelievable. The primary work of Trump's candidacy -- and his presidency -- has been to erode the idea that objective truth exists. This is an administration that said the words "alternative facts" with a straight face. And a President who has misled or lied more than 12,000 times in his tenure in the White House.

Virtually every day, Trump takes to Twitter to push ideas that are simply and provably false. No independent fact checker gives credence to the idea that Joe Biden called for the firing of Ukraine's top prosecutor to avoid an investigation into his son. There is zero evidence that the whistleblower in this Ukraine story is either a) a partisan or b) already proven wrong in his or her claims. (If anything, the whistleblower's credibility has gone up of late -- as his/her recounting of the Ukraine call was very, very close to the rough transcript released by the White House.)

But he has so conditioned his supporters to believe what he says -- and, as importantly, to reject out-of-hand anything the media reports on -- that actual facts are worthless to them. Even when -- as is the case with the Ukraine call -- the White House is the one providing the facts. The rough transcript came from the White House! The media didn't make it up. All we did is read it!

Down this road nothing good, well, lies. Because we are now not just in an age in which the media is distrusted, we are in a moment in which facts are distrusted and in which the very idea of truth is under direct assault.

This will be Trump's most lasting legacy -- whether he loses in 2020 or serves through 2024. Truth and facts are a lot like an elastic band. Once you stretch it beyond normal bound, it either breaks or never returns to its normal elasticity. That's what Trump's presidency is doing.