Let’s be honest. This one is really tough.

Yes, most Americans are disgusted by children separated from their parents and living in cages. And yes, most Americans support welcoming the Dreamers; most also back an earned path to citizenship for longtime immigrants here without documents. Trump’s policies and behavior on both issues are to his everlasting shame, and electoral disadvantage.

So what’s the problem? The problem is the flow of economic and political refugees from Central America.

On the one hand, human rights treaties legitimately require the U.S. and all other signatory countries to admit bona fide political refugees. On the other hand, many of the refugees are more economic than political and most Americans do not support open borders for all of the world’s wretched refuse, Emma Lazarus and the Statue of Liberty notwithstanding.

Every time I hear spokespeople for immigrant rights being interviewed on this conundrum, they waltz around the practical and political problem by citing treaty obligations and human decency. Not good enough.

The too-glib progressive solution is a massive regional economic development Marshall Plan for Central America, including Mexico, a policy that is necessary but not sufficient. Advocates also point out, correctly, that if Central America’s Northern Triangle is a mess, that’s substantially the fault of the United States, between American-sponsored coups, economic imperialism, and sweatshops going back a century. The Prospect recently published an eloquent piece by David Bacon documenting this shameful history.

But even if we sponsor a large-scale regional economic development plan, how exactly do we execute it in partnership with thuggish national governments without resorting to, er, regime change? In the meantime—a very long meantime—the refugee flow will only increase.

Which is why the immigration issue in 2020, despite the children’s blood on Trump’s hands, will be a tricky one for Democrats. A massive regional development plan is a proper form of restitution for all that the U.S. has done to Central America. But on the campaign trail, it sounds utopian and is not sufficiently credible as a remedy to growing flows of economic refugees right now.

I like to think that I have answers to most policy problems—remedies that depend on the right politics and then helping to build the right policy. I don’t have a good answer to this one. I hope somebody does.