On Monday, Fox News abruptly announced that the network and its star primetime host, Tucker Carlson, “have agreed to part ways” after more than a decade. The announcement came less than a week after Fox agreed to pay $787.5 million in a defamation lawsuit that prominently featured Carlson’s show and its role in spreading misinformation about the 2020 election. The news is just the latest instantiation of a broader story: In recent years, the Republican Party has morphed from a coherent institution into a fractured movement at war with itself. Conservative media, and Fox News in particular, played a central role in that shift. And now those same dynamics are tearing the conservative media ecosystem apart as well. How did we get here? How did the Tucker Carlsons of the world take over the G.O.P? And what comes next as these dynamics continue to play out? There are few scholars who have studied these kinds of questions as closely as Nicole Hemmer. Hemmer is an associate professor of history at Vanderbilt University and the author of two books about the conservative movement and media ecosystem, “Messengers of the Right: Conservative Media and the Transformation of American Politics” and “Partisans: The Conservative Revolutionaries Who Remade American Politics in the 1990s”. We released this conversation a few months ago, in January of this year, but it remains as relevant as ever. We discuss why the Cold War bonded Republicans as a party, how the 1994 Republican congressional victory inaugurated a new era of intraparty fighting, how Rush Limbaugh’s rise created a new market for far-out ideas and new pressures on conservative politicians, why conservative media has had so much more sway than liberal media over grass-roots voters, how the business model of Fox News differs from that of MSNBC and what kinds of political ideas those businesses produce, how the G.O.P. is now caught between the pincers of the donor class and the grass roots, when the chief Republican enemy became the Democratic Party, why more moderate conservatives have become so weak and more. Book Recommendations: Fit Nation by Natalia Mehlman Petrzela Dreamland by Carly Goodman Freedom’s Dominion by Jefferson Cowie Thoughts? Email us at [email protected]. (And if you're reaching out to recommend a guest, please write “Guest Suggestion" in the subject line.) You can find transcripts (posted midday) and more episodes of “The Ezra Klein Show” at nytimes.com/ezra-klein-podcast, and you can find Ezra on Twitter @ezraklein. Book recommendations from all our guests are listed at https://www.nytimes.com/article/ezra-klein-show-book-recs. “The Ezra Klein Show” is produced by Emefa Agawu, Annie Galvin, Jeff Geld and Rogé Karma. Fact-checking by Michelle Harris, Mary Marge Locker and Kate Sinclair. Original music by Isaac Jones. Mixing by Jeff Geld. Audience strategy by Shannon Busta. Special thanks to Kristina Samulewski.