A bid by Mexico to contain thousands of migrants on its southern border with Guatemala has created a major humanitarian headache for President Andres Manuel Lopez Obrador, and failed to prevent many from reaching the U.S. border en masse.
Desperate for work, fleeing poverty or violence, the Central Americans, Haitians and South Americans stuck in limbo in the southern city of Tapachula have staged protests and launched repeated attempts to break out in migrant caravans.
This month, some of them slipped past Mexican officials to join more than 10,000 migrants who crossed into . . .
