I’ve been wondering about this for a few days. As Donald Trump and the GOP establishment go through this delicate dance toward a marriage of convenience, there are two or three big policy initiatives that are usually referenced as the ones that are just unacceptable to mainstream Republicans, too crazy to be considered, unconstitutional or just too politically damaging. The most frequently mentioned are Trump’s proposed ban on Muslims entering the country and the Trump TajMaWall he says Mexico will agree to pay for.

This strikes me as odd because despite how odious these ideas are, there’s very little mention of what is undoubtedly the craziest, most dangerous, most expensive and brutal of his policies: his plan to deport roughly 3% of the current US population in 18 months.

So many of Trump’s ideas are so terrible, I hesitated to say “most” because is it really worse than banning members of an entire religion? As I said, it’s sort of like comparing serial killers. They’re all just really bad. My reason for saying it’s the worst though is that as horrible as the Muslim ban is and clearly unconstitutional, it’s not allowing in people who aren’t currently here. It’s not uprooting millions of people, dividing families, probably dumping people into countries that can’t reabsorb them.

Let’s remember the idea. Trump says he will create a “deportation force” which will round up and deport approximately 11 million undocumented immigrants in 18 months. This might not unreasonably be characterized as a war crime.

Despite just being a bad idea on numerous counts, just in very concrete terms there are credible estimates that the costs of such an operation could run to half a trillion dollars. This would also involve effectively orphaning huge numbers of children who were born in the US and thus citizens but are the children of undocumented immigrants. In some cases, it would probably mean the de facto deportation of those American citizens.

I don’t have a sufficient grasp of the numbers, geographic concentrations and so on to give hard estimates. But you cannot deport a non-trivial percentage of a country’s population and not have substantial economic dislocations, likely heavily concentrated in particular regions of the country. It is probably also true that you could not pull off this kind of operation in anything like that kind of time frame without committing numerous civil rights and civil liberties violations, not only of people with no legal status but also of lots of Americans or people here with legal status. How many people do you need to round up and at least question if not detain to weed out the 11 million who genuinely lack legal status in the United States. Many of the people in that larger haul will be white people who don’t speak with an accent? Trump has already said he’ll simply ignore the immigration courts that govern the deportation process.

These are all practical concerns. It doesn’t even get at the moral dimensions of the policy, which are ones that basically speak for itself. Does Trump still plan to do this? Do the politicians who are now supporting his candidacy support this?