Republican Sen. Ben Sasse thinks that much of what is wrong with political media today is embodied by one man: Sean Hannity.

Over the course of twenty pages in his new book, titled Them: Why We Hate Each Other—and How to Heal, the Republican senator said the Fox News primetime star is the foremost example of how—in his estimation—media personalities willfully drive a wedge between Americans of different political persuasions.

“He explained the core objective of his two different programs to the New York Times,” Sasse wrote, referring to Hannity’s television and radio programs. “It’s not to promote a particular conservative agenda, or to encourage American patriotism, or even to offer coherent arguments against liberalism. His core cause is to rage.”

Not many years ago, Sasse was beloved by conservative media personalities like Hannity.

During his bid for Nebraska Senate in 2014, The Weekly Standard dubbed Sasse’s conservative health-care positions “the real deal.” He also earned support from tea party-aligned groups, and Hannity himself predicted that if Sasse won his race he would “instantly become a leader of ideas and solutions in the Senate.”

The feeling was apparently mutual. According to a source close to Hannity, Sasse not too long ago “begged” to be on the radio program.

But President Donald Trump’s ascent to the Oval Office coincided with a deterioration of Sasse’s relationship with Hannity. The Nebraska senator has been a major critic of Trump’s rhetoric, earning Sasse fiery criticism from pro-Trump conservative media stars including Hannity, who has redefined himself over the past several years as an informal adviser and top cheerleader for the president.

Last year, Hannity declared on Twitter that “one of the biggest mistakes of my career” was supporting Sasse, whom the Fox News host described as “useless.”

Sasse dedicated nearly an entire chapter of his book, released on Tuesday, to describing how Hannity is a manifestation of political media’s downward spiral.

The Fox News star is obviously not pleased with Sasse’s attempt at media criticism. “Unfortunately, I went to bat for Ben Sasse, who has proven to be the single biggest disappointment in politics today,” Hannity reacted in a statement to The Daily Beast. “He totally conned me like he conned the people of Nebraska.”

Dubbing Hannity-like programming as “ polititainment ,” Sasse described in the book his Trump-era clashes with the Fox host as “unusually unpleasant,” and laid out several examples of what he saw as failures of Hannity to inform the public in good faith.

The Nebraska senator said most storylines on the top-rated Fox News show could be broken down to a simple formula: “Liberals are evil, you’re a victim, and you should be furious.”

“Hannity tells a lot of angry, isolated people what they want to hear,” Sasse wrote. “And he has the delivery down to an art form. We’d all be better off, as would our communities, if we understood the game he and his colleagues—on both sides of the spectrum—are playing.”

Sasse continued to write that Hannity hypocritically criticized the Nebraska senator’s cyber-security positions despite conducting “fawning” interviews with WikiLeaks founder Julian Assange.

He also knocked Hannity for politicizing the mass shooting at the Route 91 Harvest Festival in Las Vegas last year, pointing out that the Fox News host never corrected a broadcast in which he cited a fake Twitter account to claim the social-media site’s users were overwhelmingly cheering on the possibility that mainly Trump supporters were killed at the country-music festival.

“Having given his millions of viewers the impression that Trump supporters were killed and that liberals cheered it, he moved on,” Sasse said. “It was a grotesque distortion of reality. It was, quite literally, fake news.”

Sasse also dished on several conversations he had about Hannity with Fox News employees and his fellow senators.

One of his fellow lawmakers, Sasse wrote, described Hannity’s programming as “‘Hey-can-you-believe-this- shit?!’ messaging.” The senator recalled how an unnamed Fox News personality told him that “Hannity hasn’t been a conservative in years,” and that the Fox star “figured out long ago that teaching and defending conservatism is both harder and less effective than just hitting some crazy liberal.”

“ [Hannity’s] core objective is... not to promote a particular conservative agenda, or to encourage American patriotism, or even to offer coherent arguments against liberalism. His core cause is to rage. ” — Sen. Ben Sasse (R-NE)

Sasse repeatedly emphasized that Hannity is integral to a dysfunctional media environment that rewards conflict and scandal.

The senator claimed that “both sides” of the political spectrum are guilty of media exaggeration for political gain: He compared right-wing outlets’ penchant for obscure campus-outrage stories with left-leaning media outlet’s stories on racist comments made by relatively unknown Trump supporters.

Sasse blamed media audiences for consuming such salacious content, which, he said, in turn drives media organizations to relentlessly focus on such types of stories. “The incentive structure in the media complex rewards pushing the gas, not tapping the brakes—or qualifying a point,” the senator wrote, donning his media-critic cap. “Celebrities, political big shots, and media outlets have junior staffers constantly tweeting and posting, giving readers new reasons to click—and the sharper-tongued the post, the better.”

But Sasse mostly singled out conservative media, which he said he has interacted with more by virtue of being a conservative politician and news consumer. He suggested that the right-wing media environment is driven largely by deference to an audience that tolerates only pro-Trump content.

Sasse remembered how, after being “shellacked” on-air for his anti-Trump views, a conservative host told him it was “just a game.”

“The hosts couldn’t afford to lose a quarter or a third of their audience, so they attacked any Republican who questioned President Trump,” Sasse explained. “They wanted to know if I was angry at their spin.”

“‘You get it, don’t you?’ one of them said, smiling at me. ‘You understand why I have to hit you?’” Sasse recalled.

“I didn’t.”