Eventually, Klein argues, the polarization has resulted in a country where large numbers of people fear a kind of coming apocalypse at the hands of those with which they disagree.

Thus, in Klein's eyes, the two parties represent fundamentally different types of people to which, due to this identity fusion, frustrating conflict becomes inevitable.

He argues that modern journalism has fed into a deleterious feedback loop, with attempts to actually persuade individuals generating far less interest than material meant to feed partisanship.

[5] She notes that Klein marshals an "impressive body of evidence" to bolster his view that partisan identity has become central to "psychological self-expression", and praises how he "takes into account a multitude of factors" underlying political polarization, including "institutional, cultural, and psychological" factors, faulting him only for his "surprisingly dismissive" consideration of class.

Publishers Weekly praised the author's "pithy assessments" and "thoughtful, evenhanded outlook" on polarization; however, they stated that readers may be disappointed by the "modest" solutions he sets forth in the book.

To Metcalf, "Klein, ultimately, cannot square his desire to nudge the polity back toward capital-L Liberalism—the creation of a polis built on the dialogue of free citizens with one another—with his inclination to offer capital-E Explanations for our political behavior.

[10] In Dissent, political scientist Daniel Schlozman says that the book is a "persuasive account of polarization's rise", but semi-derisively labels the book a "well-read amateur’s tour of what scholars have to say about group psychology and political behavior" and states that it "ultimately fails to account for our deepest divides", in particular criticizing its lack of attention to power dynamics, resulting in Klein letting "the ruling classes off easy".

[11] In Jacobin, Sohale Andrus Mortazavi lauds Klein's analysis of the systemic effects of polarization on American democratic structures, calling it "convincing" and "grounded in material reality".

[15] He describes the book as "a little like reading a policy explainer on Vox: everything seems at once comprehensive and reasonable and consequential, but on closer inspection there are major omissions and unresolved contradictions", and points to "a good deal of ahistorical nonsense to bring his argument to the desired consistency".

[13] He faults Klein in particular for what he sees as an overly simplistic division "between 'hope,' on the one hand, and a revanchist yearning to keep out Muslims and Mexicans, on the other", asking whether radicalization within the Republican Party is not all the result of "whites’ fear of America becoming a majority-minority nation", but also a reaction "to the Democratic Party's own radicalization—its wanton use of race as a weapon, its quick acceptance of every new fad in sexual identity, its embrace of the self-hating ideologies prevailing on elite college campuses".