Make no mistake: if the caravan reaches the U.S. border, it will be a disaster on several levels. At the most basic level, it will be a humanitarian crisis. Depending on where groups of migrants decide to cross, food, water, and exposure will be an immediate problem. Vast stretches of the U.S.-Mexico border are sparsely populated and geographically harsh. Facilities to house and feed hundreds of families for more than a day or two simply do not exist along the border. Most of those who manage to cross into the United States would have to be released before long.

While Border Patrol is dealing with all that, drug cartels would no doubt take advantage of the situation. While I was on a reporting trip to the Rio Grande Valley last month, Border Patrol agents told me that when unaccompanied minors began showing up in large numbers in 2014, it swamped their resources and left vast stretches of the border un-monitored. Drug cartels sent over large groups of minors on purpose, they said, as a diversionary tactic. A group of 80 or 90 children and families surrendering to Border Patrol would tie up every agent in that area for the entire day, allowing smugglers to ferry drugs across an unguarded border with impunity.

All of this would in turn trigger a political crisis that very well might accrue to Trump’s advantage. In some ways, the caravan is the worst possible development for Democrats, who have painted themselves into a corner on immigration by betting the future of their party on a rigid form of identity politics. For much of the Democratic Party’s base, “border security” is tantamount to racism.