When I said yesterday that there’s nothing this guy enjoys more than a good “that’s not who we are” lecture, I wasn’t joking. He uses almost those exact words in this broadside at the White House.

I’m gonna guess this is worth about seven or eight points to Trump in terms of public support. Without Obama weighing in, figure 70/30 or so opposed to deporting DREAMers. With Obama weighing in, maybe 62/38-ish. That’s how many Republicans will rally to Trump purely out of annoyance at a vintage O scolding about what sort of opinions it is and isn’t “American” to hold.

[B]ecause it made no sense to expel talented, driven, patriotic young people from the only country they know solely because of the actions of their parents, my administration acted to lift the shadow of deportation from these young people, so that they could continue to contribute to our communities and our country. We did so based on the well-established legal principle of prosecutorial discretion, deployed by Democratic and Republican presidents alike, because our immigration enforcement agencies have limited resources, and it makes sense to focus those resources on those who come illegally to this country to do us harm. Deportations of criminals went up. Some 800,000 young people stepped forward, met rigorous requirements, and went through background checks. And America grew stronger as a result.

But today, that shadow has been cast over some of our best and brightest young people once again. To target these young people is wrong – because they have done nothing wrong. It is self-defeating – because they want to start new businesses, staff our labs, serve in our military, and otherwise contribute to the country we love. And it is cruel. What if our kid’s science teacher, or our friendly neighbor turns out to be a Dreamer? Where are we supposed to send her? To a country she doesn’t know or remember, with a language she may not even speak?…

Ultimately, this is about basic decency. This is about whether we are a people who kick hopeful young strivers out of America, or whether we treat them the way we’d want our own kids to be treated. It’s about who we are as a people – and who we want to be.

He’s still telling the old lie that DACA is nothing more than “prosecutorial discretion,” eh? If that were true, all it would mean is that DREAMers end up at the bottom of the list of DOJ’s and DHS’s immigration priorities. In reality DACA means much more, most notably eligibility for a work permit. In a legal quirk, it can also entitle recipients who leave the country and then re-enter to green-card status and eventually citizenship. Ironically it’s Trump who may end up exercising true “prosecutorial discretion” with respect to DREAMers, stripping them of any legal right to stay and work but making them the lowest possible priority for removal.

I do think there’s strategy here on Obama’s part, though, as I wrote yesterday. He probably believes, not incorrectly, that this is a winning issue for Democrats if they can maneuver the GOP into strong opposition. The media will be filled with sob stories from DREAMers; there’ll be highly public divisions within the party itself, with amnesty fans like McCain and Graham pitted against border hawks; and the more attention the issue gets, the more Republicans will be consumed with it instead of, say, with returning to health-care reform. (And the window for that is shrinking if McConnell wants to do something via reconciliation.) Right now there’s a chance that Trump will be able to muscle enough grassroots support on the right for a compromise involving a DREAM amnesty that the issue will be largely defused for Republicans. Obama’s entry into the fray complicates that. Trump will inevitably lash out at him on Twitter for having created this legal and constitutional mess in the first place; nationalists will use Obama’s support as a rallying point against legalizing DREAMers by any means, not just against DACA; and soon Ryan and McConnell will be stuck trying to broker some sort of deal without much public support from the president, all but guaranteeing failure. Then Democrats will use that against Republicans next fall. Obama’s criticism is basically a grenade rolled into the GOP tent, and he knows it. I’m surprised he didn’t single out Trump by name, just to make this extra provocative. Presumably presidential “decorum” required that he not do so.

To give you a sense of the battle that’s coming, here’s populist favorite Kris Kobach proposing that DREAMers leave the country and get in line for readmission. Having big-name border hawks like him, Sessions, and Miller all pushing the idea that DREAMers are sucking jobs away from American citizens is going to harden Trump’s own view of them, possibly creating a scenario where Trump doesn’t want to sign a DREAM amnesty even after he publicly urged Congress to deal with the problem. The worst thing Ryan and McConnell can do to him at this point is to actually produce a bill and send it to his desk. I wonder if, as Trump’s relations with congressional Republicans deteriorate, they’ll end up doing exactly that and letting Trump deal with the fallout. Imagine a standalone DREAM amnesty being sent to the president for signature. It’s all on Trump at that point.