Honduran migrants board a truck in Mexico as they take part in a caravan heading to the United States. (Johan Ordonez/AFP/Getty Images)

WITH EACH passing day, President Trump makes clearer his delight in the political advantage he may extract from the migrant caravan heading north through Mexico. His enthusiasm for forging a genuine solution to the immigration problem at its source? Not so much.

In fact, judging from Mr. Trump’s Twitter feed, the president seems more inclined to exacerbate the problem — by cutting off U.S. aid to Central America, thereby deepening insecurity and misery there. Those are the very factors that have driven the recent spike in migration, especially by parents and children.

On Monday, Mr. Trump began his tweeting day by citing what he called the “National Emerg[enc]y” posed by the caravan, which he blamed falsely on Democrats for failing to pass unspecified immigration laws, and on “unknown Middle Easterners” mixed in with the caravan, of which there is zero evidence. He concluded by saying the administration would now sever, or substantially reduce, foreign aid to El Salvador, Guatemala and Honduras.

That’s a prescription for more migration, not less. Even in war-torn and impoverished places, people leave their homes and communities reluctantly, abandoning their property, familial roots and sense of belonging only under extreme economic or physical duress. U.S. aid to Central America is a tiny percentage not just of overall government spending but also of foreign aid generally, but it is critical to countries that are grappling with enormous hardship and migrant outflow.

According to Reuters, the Trump administration already has taken steps to slash official aid to El Salvador, Guatemala and Honduras, which totaled just under $300 million in 2016, by nearly 40 percent by 2019. The cuts would diminish economic opportunity and reduce the ability of ordinary people to feel safe in their neighborhoods from drug gangs and crime. Undercut local law enforcement along with a sense that people can improve their lives, and rest assured: Many more Central Americans will seek a better life in the United States.

An additional severe blow is the administration’s decision to cancel temporary work permits and legal status for about 250,000 Salvadorans and Hondurans living in the United States, forcing many of them to leave or be deported over the coming year, thereby stanching the flow of funds they send home to their families.

A more rational policy would double down on U.S. aid programs, with a focus on crime-fighting and security, while allowing would-be migrants to apply and be screened for asylum in their home countries. That could avoid the spectacle of north-bound caravans, such as the one making its way through Mexico right now — and of a president for whom the misery of migrants is just a convenient wedge issue.