No, he can’t deport all illegal immigrants, I write in my latest column. But that doesn’t mean he should settle for tinkering with the system:

A reasonable benchmark is the size of the illegal-immigrant population in the United States, most recently estimated by the Department of Homeland Security to include 11 million people. If that number appreciably shrinks — and not because of a recession — Trump will have delivered on his promise. He will also have proved that illegal immigration is not an inexorable force and that government won’t just ignore voter demands on the issue forever. If that number doesn’t shrink, on the other hand, it will be fair to conclude that Trump’s presidency failed at one of his main goals.

I go on to suggest how that goal can be met.