“Words matter.” Hillary Clinton directed these two words at Donald Trump in the closing minutes of their first presidential debate. Clinton was referring not only to Trump’s frequent untruths—Politifact deemed that 66 percent of his statements at that debate were false or mostly false—but also to his propensity for floating political trial balloons with little regard to their global ramifications. In May, for example, Trump implied that he might force creditors to accept less than full payment on government debt, shaking the financial community. Trump’s suggestion in July that the U.S. could abandon its NATO allies “fueled angst” across Europe and Asia. His praise of tyrants, his suggestion that more countries acquire nuclear weapons, and his cries of a rigged election are all examples of Trump’s extraordinarily loose and cynical political language, a style of public speech that is unprecedented for a modern presidential candidate.

But this style did not start with Trump, of course. It’s the result of a steady devolution of American public discourse that has been most prevalent on the political right. The American right has shown itself to be less wedded to facts and precision in its political speech for at least two decades. Two separate analyses of the three major cable news networks—CNN, MSNBC, and Fox News—found that Fox, the channel most conservatives watch, was by far the least truthful of the three. Multiple studies have found that people who get their news only from Fox know less about the world than people who watch no news at all. Trump’s make-it-up-as-he-goes speaking style was made possible, in fact, by a conservative media strategy that enjoins followers to reject the untrustworthy liberal media, while feeding those followers a steady diet of falsehoods and half-truths. With the rise of Trump, some Republicans are beginning to rue the strategy.

In June, the conservative radio host Charlie Sykes stated that the right’s twenty-year assault on the mainstream media had in fact fueled Trump’s rise, opening the door to his ability to lie so frequently without losing support. Lamenting how difficult it had become to refute the outlandish assertions of some of his own listeners, Sykes said: "At a certain point you wake up and you realize you have destroyed the credibility of any credible outlet out there. And I am feeling that, to a certain extent, that we are reaping the whirlwind of that. I have to look in the mirror and ask myself, ‘To what extent did I contribute?’”

Sykes offered an example: "Let's say that Donald Trump basically makes … whatever claim he wants to make, and everybody knows it's a falsehood. It is impossible for me to say to my audience, ‘By the way, you know that's false.’ They'll say, ‘Why? I saw it on Allen B. West.’ Or they’ll say, ‘I saw it on a Facebook page.’ And I'll say, ‘The New York Times did a fact check.’ And they'll say, ‘Oh, that's The New York Times. That's bullshit.’ There’s nobody—You can't go to anybody and say, ‘Look, here are the facts.’” Sykes added that he felt pressured to repeat lies: “If I don't say these things from some of these websites, then suddenly I have sold out. Then [my listeners] will ask what's wrong with me for not repeating these stories I know not to be true."

John Ziegler, another conservative radio host, and the blog RedState both agreed in part with Sykes' comments, and they bolstered an argument some on the left have been making for years. In its twenty-year delegitimization of the main-stream media, the right-wing media has not only degraded the credibility of the entire media but also degraded the idea that objective facts even exist. The message from the conservative media over this period has been: if a press outlet bolsters conservative ideology, then what it is saying is true; if it bolsters liberal ideology, it's false. That's nonsense, of course (as is the reverse), but even worse is that from here it becomes a very short leap for a demagogue to say, "The entire media is crooked!” Then you've reached a point where any outlet that falls into disfavor can be branded part of the “crooked media.” The demagogue’s message becomes: “I am the only one you can trust.”

In an insightful new book by Mark Thompson, ++Enough Said: What's Gone Wrong With the Language of Politics? ++ [https://www.amazon.com/Enough-Said-Whats-Language-Politics/dp/1250059577/ref=sr_1_1_twi_har_1?s=books&ie=UTF8&qid=1478275612&sr=1-1&keywords=enough+said], Thompson argues that a key reason contemporary journalists and politicians are held in such low regard is because they spend so much time lambasting their own professions. Thompson notes that in recent decades “politicians got into the habit of calling each other liars and phonies with almost as much vehemence as the insurgents,” which, as far as the public was concerned, wasn’t “just excoriating their immediate opponents, they were damning an entire profession.” He adds that, “The near universal trashing of the regular language of politics creates perfect conditions for the true demagogue.”

This “trashing of the regular language of politics” and the delegitimization of the mainstream media have indeed been a boon to the purveyors of misinformation. Just look at the debate over climate change. There have been at least two surveys that concluded that 97 percent of climatologists agreed that human-caused climate change is real and a serious threat. Thompson cites a review of more than 64,000 peer-reviewed papers which found that just four disagreed with the majority. If that’s not consensus, there’s no such thing. Yet while most mainstream outlets accurately report the consensus, the right-wing media continues to tell its followers that significant scientific doubt remains, or that the scientists are purposely skewing the evidence. The result is that more than half of Republicans still don’t believe the climate is even changing, let alone that humans are causing it. Trump has Tweeted that “the concept of global warming was created by and for the Chinese.”

In an enlightened democracy, science should remain above politics, an objective arbiter whose decrees can serve as a final word in the often confounding battle of ideas between left and right. But in our current state of devolved political speech, even science is under attack. Thompson points to the climate debate as a key indicator that our political speech is “headed toward crisis.”

“Science is meant to be the decider,” he writes, “a species of knowledge that stands above the fray and whose pronouncements should be listened to and acted upon without delay.” The danger in the right’s attempt to delegitimize climate science, Thompson argues, is not only that it will delay efforts to reduce carbon emissions, but also that unscientific “perspectivism” will then bleed into other areas of public discourse. “If the authority of science no longer carries the day, then why should we accept any other branch of specialist knowledge? Why should we believe what the economists and social scientists and government experts tell us? Or accept the decisions of the courts? After all, if knowledge counts for nothing and everything is a matter of opinion, we’re all experts.”