It’s unclear how effective that would be. Many of the immigrants in the caravan are asylum seekers. Closing ports of entry would just delay the US’s obligation, under its own laws, to consider their applications for asylum. And, the US government doesn’t have the personnel or the resources to entirely seal the places in between the ports of entry.

How much trade comes through the US-Mexico border?

What the president can safely assume are billion-dollar losses for American companies, particularly manufacturers, importing and exporting to Mexico. In a single month—July 2018, the last for which data is available—$41.5 billion’s worth in goods crossed the border, about 40% of them flowing south.

Even temporary disruptions at the border—for example, increased scrutiny at the Canadian border after 9/11, and the closure of the San Ysidro port of entry in San Diego due to construction last year—can cause massive delays and hurt business, says Sarah Pierce, a policy analyst at the Migration Policy Institute.

Who would be hurt by closing the US-Mexico border? 

In his morning tweets, Trump indicated that he’s willing to sacrifice trade in the name of homeland security.

But would his party agree? Most of the states that would be affected if he closed the border were ones that voted for him, and Republicans are relying on those states for the midterm elections.

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