Arrests for illegal border crossings into the United States dropped again in December 2019, the seventh consecutive month they have declined. The fact you probably haven’t heard about this in the media is likely because it is a big win for President Trump — and that’s one reason why so many Trump backers have tuned the media out. The migration saga started last summer. Hundreds of thousands of poor Central Americans made the 1,000-mile-plus journey north fueled by the belief it was easy to get into the United States. By June, US border agents were arresting more than 130,000 people a month. Something had to be done to prevent a humanitarian disaster. Trump acted. He announced he would levy tariffs on goods from Mexico unless that country did more to stem the flow of Central Americans seeking asylum in the United States. The move was widely condemned by the usual suspects, but once Mexico submitted to Trump’s demands, attention moved elsewhere. It turns out that the critics were wrong. Fewer than 33,000 were arrested at the southwest border in December. That’s not only 100,000 fewer people than were arrested in May right before Trump acted; it’s nearly 18,000 people fewer than in December 2018. It’s not as though the countries the migrants were fleeing suddenly became garden spots overnight. There’s only one explanation for the rapid decline: Trump’s policies worked.