Political leaders from a dozen countries have gathered in Mexico City to discuss a key question: How can the left win?

The shutdown in Mexico City began about 2 p.m. local time and lasted about 20 minutes as hundreds of union members marched to the airport’s entrances.

Mexico’s Supreme Court building in Mexico City. Mexico’s shift away from an appointment-based system to the election of judges has, at least for now, amounted to a crucial step in Morena’s ...