In Talk Radio's America Brian Rosenwald traces talk radio's growth across the late twentieth and early twenty-first centuries. He suggests that Rush Limbaugh's “national radio debut” on “August 1, 1988, marked the beginning of the long road to President Donald Trump” (1). Rosenwald proposes that talk radio transformed the modern Republican Party by pushing it towards conservative hegemony, by railing against any dilution of right-wing principles. Many Republicans increasingly viewed hosts like Limbaugh or Sean Hannity, and their passionate listeners, as key constituents to court (2–10).

Rosenwald convincingly demonstrates how, throughout the 1990s, 2000s, and 2010s, talk radio championed ideological purity and hounded Republicans who pursued moderation, pragmatism, or bipartisanship. He sees the insular, almost uniformly conservative nature of present-day Republicanism – which has set up camp alongside right-wing media outlets – as the culmination of talk radio's impact (51–55, 61–70, 104–14, 121–25, 133–49, 168–212).

One of the book's strengths is the tangible examples Rosenwald gives illustrating talk radio's bearing on the “nuts and bolts of politics and policymaking” (4). He describes talk radio's success in defeating the 1994 Lobbying Disclosure Act. Hosts stoked antagonism to the bill – which would have helped curtail lobbyists’ influence –among listeners who, in turn, pressured Republican lawmakers to stop the Act or risk defeat in the upcoming mid-terms (64–67). Rosenwald also illustrates how talk radio has given succour to the Grand Old Party's fringes, especially conservative primary challengers to mainstream Republicans. Hosts encourage listeners to support contenders or donate to their campaigns, with talk radio often providing a venue for outsiders to spread their messages. Rosenwald credits talk radio for the upset primary victories of Christine O'Donnell in Delaware (2010) and Richard Mourdock in Indiana (2012). The fact that both lost in general elections is irrelevant to hosts, Rosenwald suggests, who are more concerned with the GOP's ideological colouring than its electoral fortunes (185–205). Rosenwald perceptively demonstrates awareness of the multidirectional relationship between talk radio and the GOP. While exploring talk radio's power to influence Republicans, out of fear that hosts might marshal opposition to them, he acknowledges how many Republicans utilized – and continue to utilize – the medium to curry favour (80–90, 181).

While talk radio giants like Limbaugh or Hannity, and leading conservatives like Newt Gingrich, are noteworthy parts of Rosenwald's analysis, he also integrates behind-the-scenes actors like station managers and owners or political media strategists. He similarly discusses crucial external factors like law changes, syndication, or technological advances. Exploring the importance of the 1987 repeal of the fairness doctrine, the proliferation of cellular phones, and the rise of the Internet enables Rosenwald to give a fuller picture of talk radio's evolving significance (16–21, 81–84, 109–12, 143, 189–92).

Quantifying audience reactions to talk radio in greater depth would have strengthened Rosenwald's work. He asserts that, “Instead of manipulating fans, talkers harnessed their collective views and brought them to bear on issues, legislation, and politicians the audience otherwise might not notice. This … in turn, shaped listeners’ perceptions and stirred their passions” (256–57). While he does offer snippets of reaction, such as Andrew Breitbart's claim that tuning into Limbaugh transformed his liberal views, it is difficult for Rosenwald to ascertain exactly what impact talk radio did and did not have on listeners – or whether talk radio moulded or mirrored public attitudes (173). Rosenwald himself notes that audiences were not monolithic. A 1996 study found that 47.8 percent of Limbaugh's listeners identified as conservative, 34.1 percent as moderate, and 18.1 percent as liberal (80). Given the difficulties in accessing and assessing listeners’ responses, some might dispute the particular credit he gives to talk radio for affecting change.

Rosenwald's work is a timely reflection for an America where conservative media have mushroomed and polarization seems entrenched. “Trump's election signalled that Americans now lived in the world talk radio made. That was the only world in which President Donald Trump was possible”, he declares (248). Throughout the book's concise, digestible chapters, Rosenwald grapples with contemporary political, media, and cultural realities that seem obvious. He offers a compelling history for those seeking to understand how the United States has become both “talk radio's America” and Donald Trump's America.