The Senate is where Joe Biden’s agenda will live or die. More specifically, the intricacies of archaic Senate rules — the budget reconciliation process, the filibuster, the majority leader’s ability to control the floor — combined with the fealty today’s senators have to yesterday’s structures will decide the agenda’s fate. It would be the gravest mistake for progressives, or anyone else, to consider the fight over how the Senate works to be a sideshow compared with debates over a $15 minimum wage, a Green New Deal or democracy reform. The fight over how the Senate works is what will decide all those other debates. Adam Jentleson served as deputy chief of staff to Senator Harry Reid when he was the majority leader. Jentleson was high enough to see how the institution really worked, and young enough to be free of gauzy nostalgia from the days of yore. And his book, "Kill Switch: The Rise of the Modern Senate and the Crippling of American Democracy," is both blistering and persuasive. “This is not a particularly uplifting history,” Jentleson writes. But nor is it without hope. “Unlike many of the structural features that determine the politics of our era, the Senate is relatively easy to reform.” So I invited Jentleson on my podcast, “The Ezra Klein Show,” to explain how the modern Senate really works, why it works that way, and how to fix it. Along the way, we discuss what can — and crucially can’t — be passed through budget reconciliation, why senators like Joe Manchin and Kyrsten Sinema continue to defend the filibuster (and why Jentleson thinks they will change their minds), the foundational myths of the Senate, like the idea that the modern filibuster encourages compromise, how Mitch McConnell understands the American political system better than his opponents and much more.