Republicans want to label Kamala Harris as the border czar. And by just looking at a chart, you can see why. Border crossings were low when Donald Trump left office. But when President Biden is in the White House, they start shooting up and up — to numbers this country had never seen before, peaking in December 2023. Those numbers have fallen significantly since Biden issued tough new border policies. But that has still left Harris with a major vulnerability. Why didn’t the administration do more sooner? And why did border crossings skyrocket in the first place? Harris was not the border czar; she had little power over policy. But to the extent that there is a border czar, it’s the secretary of homeland security, Alejandro Mayorkas. So I wanted to have him on the show to explain what’s happened at the border the past few years — the record surge, the administration’s record and what it has revealed about our immigration system. Book Recommendations: The Nickel Boys by Colson Whitehead String Theory by David Foster Wallace The Dictionary Thoughts? Guest suggestions? Email us at [email protected]. You can find transcripts (posted midday) and more episodes of “The Ezra Klein Show” at nytimes.com/ezra-klein-podcast. 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 Rollin Hu. Fact-checking by Michelle Harris, with Mary Marge Locker and Kate Sinclair. Our senior engineer is Jeff Geld. Our senior editor is Claire Gordon. The show’s production team also includes Annie Galvin, Elias Isquith, Kristin Lin and Aman Sahota. 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 Ariel G. Ruiz Soto, Dara Lind, David Frum, Jason De Léon, Michael Clemens, Natan Last and Steven Camarota.