Last week on the show, I argued that the Democrats should pick their nominee at the Democratic National Convention in August.

It’s an idea that sounds novel but is really old-fashioned. This is how most presidential nominees have been picked in American history. All the machinery to do it is still there; we just stopped using it. But Democrats may need a Plan B this year. And the first step is recognizing they have one.

Elaine Kamarck literally wrote the book on how we choose presidential candidates. It’s called “Primary Politics: Everything You Need to Know About How America Nominates Its Presidential Candidates.” She’s a senior fellow in governance studies and the founding director of the Center for Effective Public Management at the Brookings Institution. But her background here isn’t just theory. It’s practice. She has worked on four presidential campaigns and 10 nominating conventions for both Democrats and Republicans. She’s also on the convention’s rules committee and has been a superdelegate at five Democratic conventions.

It’s a fascinating conversation, even if you don’t think Democrats should attempt to select their nominee at the convention. The history here is rich, and it is, if nothing else, a reminder that the way we choose candidates now is not the way we have always done it and not the way we must always do it.

Book Recommendations:

All the King’s Men by Robert Penn Warren

The Making of the President 1960 by Theodore H. White

Quiet Revolution by Byron E. Shafer

Thoughts? Guest suggestions? Email us at ezrakleinshow@nytimes.com.

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.

This episode of “The Ezra Klein Show” was produced by Annie Galvin. Fact checking by Michelle Harris, with Kate Sinclair and Kristin Lin. Our senior engineer is Jeff Geld. Our senior editor is Claire Gordon. The show’s production team also includes Rollin Hu. Original music by Isaac Jones. Audience strategy by Kristina Samulewski and Shannon Busta. The executive producer of New York Times Opinion Audio is Annie-Rose Strasser. And special thanks to Sonia Herrero.