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.

Mayorkas joined me for a conversation on my podcast. This is an edited transcript of our conversation.

Ezra Klein: We had a significant surge in migrants at the southwestern border during the first three years of the Biden administration. We saw that peak at about 300,000 encounters last December, the most ever recorded. What made so many more people decide to take the dangerous journey to the United States between 2021 and 2023?

Alejandro Mayorkas: We have to put that question in its historical context. First and foremost, it is the postpandemic years — I should say the peak year of 2020. And there was a tremendous pent-up desire to leave the conditions in which people found themselves — violence, financial insecurity, corruption, extreme weather events, totalitarian or authoritarian regimes, the consistent drivers of displacement.