Well, it was bound to happen eventually: Donald Trump has finally made a genuinely useful contribution to the public debate.

In an interview with CNN, Trump went farther than I’ve seen any Republican presidential candidate go on immigration, explicitly pledging to carry out the mass deportation of all undocumented immigrants:

Trump said Wednesday in an interview with CNN’s Dana Bash that as president he would deport all undocumented immigrants and then allow the “good ones” to reenter the country through an “expedited process” and live in the U.S. legally, though not as citizens.

“Legal status,” Trump suggested. “We got to move ’em out, we’re going to move ’em back in if they’re really good people.”…

Trump would not say how he would locate, round up and deport the 11 million undocumented immigrants he says must go. Instead, he deflected, saying that while it may be a task too tall for politicians, it isn’t for a business mogul like himself.

“Politicians aren’t going to find them because they have no clue. We will find them, we will get them out,” Trump said. “It’s feasible if you know how to manage. Politicians don’t know how to manage.”

And when asked about whether he would deport undocumented immigrants who came to the U.S. as children, Trump fumbled and said, unsure, that “it’s a tough situation” and “it depends.”

After watching Trump’s full comments, which are garbled and crazy (shocking, right?), I think the above description is about right. In response, Ed Kilgore joked that it’s time to “bring on the cattle cars” to facilitate mass deportation, and added:

Estimates of the cost of mass deportation of the undocumented start at about $265 billion and range on up from there….Now that Trump’s forced this issue right out in the open, it’s time for us all to ask him and other Republicans who won’t endorse a path to legalization exactly how much they are willing to spend in money and in lost civil liberties to implement their plans. No sense weaseling around and dog-whistling this issue any more.

One wonders how large a Cattle Car Caucus there really is in Congress. Republicans have voted to roll back Obama’s executive actions shielding millions from deportations, but many have premised their opposition on legalistic and separation-of-powers grounds, which is a legitimate case to make (the courts may side with it), even if one disagrees with it. But broadly speaking, Republicans who oppose legalization have not been meaningfully pressed on the full implications of that opposition, i.e., do they believe all of the undocumented should be removed? If so, how do we go about doing this? If not, do we just leave them in the shadows, and why would that be better for the country than legalization with penalties would be?

Businessman and TV personality Donald Trump is a possible Republican contender for the White House in 2016. Here's his take on Obamacare, building a border wall, and more, in his own words. (Julie Percha/The Washington Post)

And on that score, Ed is right to hope that Trump has now forced this issue out into the open. Indeed, one hopes that the moderators of the upcoming GOP debate will see an opportunity in Trump’s cattle car musings: why not ask all the GOP candidates whether they agree with him? And if not, where do they stand on the 11 million exactly? Remember, Mitt Romney’s big “self-deportation” moment came at a GOP primary debate. So perhaps the moderators will see an opportunity here to make a similarly newsy splash.

A discussion of this topic could prove very valuable. It’s a discussion you’d think conservatives would want, too. It’s certainly possible you could see Ted Cruz and Trump use such a discussion to try to knock Jeb Bush down a few pegs. Both Cruz and Trump favor legal immigration, and perhaps they could continue advocating for that while insisting that the rule of law requires removal of all illegal immigrants. But it’s not at all clear how many GOP candidates would agree with Trump here.

What about Scott Walker? He has previously supported comprehensive immigration reform but has since moved to the right on the issue, and he has also said undocumented immigrants need to return to their “country of origin and then get in line.” So he may demur and say he supports legal status, once the border is secured. What about Marco Rubio, who championed the Senate bill, but is now in the border-security-first camp? Maybe somewhere to the left of that.

And Jeb Bush? Well, given that he has already called on fellow Republicans to allow that most illegal immigrants face a morally complex plight — and that they have something positive to contribute to American life — this could perhaps provide him an occasion to stage the grand confrontation with Trump that some Republicans think is inevitable.

It would also be really interesting to see how GOP primary voters react to such a discussion. One recent poll showed that 63 percent of Republicans want the focus of immigration policy to be not on legalization, but on “stopping the flow of illegal immigrants into the U.S.” and “deporting those already here.” That finding may have been inflated by the border security component of this question wording; a discussion of these issues could help flesh out where Republican voters really are on them.

The point is that eventually, we’ll need to hear from all the GOP candidates as to what they would do about the 11 million — beyond vaguely supporting legal status, but only after some future point at which we’ve attained a Platonic ideal of border security. Trump may have just made it more likely that this moment will come sooner, rather than later. One can hope, anyway.