In the run-up to the 2016 midterm elections, President Trump spoke frequently about the threat posed by the “migrant caravan,” a group of Central and South American migrants travelling through Mexico toward the U.S. border. In the past two weeks, the caravan has arrived in the Mexican border city of Tijuana. On Sunday, U.S. border agents deployed tear gas on a group of migrants attempting to cross the border, including a number of children. Reporting from Tijuana, Jonathan Blitzer speaks to David Rohde about the situation at the border and about how the Trump Administration is reshaping American immigration law.