Beto O’Rourke Moves Toward a 2020 Race He Could Upend, Ready or Not

Beto O’Rourke has driven alone across the plains, straining to find his emotional bearings — or at least a Pancake House in Liberal, Kan. He has collected an “El Pasoan of the Year” award, before a modest audience, and smiled coyly through an interview with Oprah Winfrey, before a bigger one.

He has surfaced on college campuses, to listen to students; at a Metallica concert, to listen to Metallica; and at the premiere of a documentary about his star-making Senate run in Texas at the South by Southwest festival, to...