In January, during the longest government shutdown in America’s history, President Donald Trump rode in a motorcade through Hidalgo County, Texas, eventually stopping on a grassy bluff overlooking the Rio Grande. The White House wanted to dramatize what Trump was portraying as a national emergency: the need to build a wall along the Mexican border. The presence of armored vehicles, bales of confiscated marijuana, and federal agents in flak jackets underscored the message.