President Trump arrives for a meeting with House Republicans on Tuesday. (Matt McClain/The Washington Post)

In the strange era that has been the Trump presidency, perhaps no policy debate has been as strange as immigration. For the second time now, President Trump has taken an action he claims he dislikes but the law requires, then proceeded to use it as a bargaining chip. First it was DACA; now it's separating families at the U.S.-Mexico border.

In both cases, Trump has essentially held hostage popular things he claims to side with everyone else on in the hope of obtaining things that are considerably less popular, like border security and a wall.

And in both cases, Congress could call his bluff — if it had the will.

The practice of separating families at the border has been denounced by most members of Congress, and on Tuesday Senate Majority Leader Mitch McConnell (R-Ky.) said every GOP senator wanted to bring the practice to an end. Okay, you might think, then why not just pass a bill to stop it?

They appear to be looking at that, with Sen. Ted Cruz (R-Tex.) late Monday releasing the outlines of a bill that would halt the practice by doubling the number of federal immigration judges, expediting hearings and creating temporary shelters. Sen. John Cornyn (R-Tex.) is also crafting a bill, and there is talk of a bill that would temporarily stop the separations of families in the meantime. McConnell said Tuesday that he's looking to vote on such a bill by the end of the week.

But Trump doesn't exactly appear thrilled with the idea.

Speaking in front of small-business owners on Tuesday, Trump decried the idea of adding more judges, as Cruz's bill would do. “Ultimately, we have to have a real border, not judges,” Trump said. “Thousands and thousands of judges, they want to hire. Who are these people? When we vet a single federal judge, it goes through a big process.”

He added: “We don't want judges; we want security on the border.”

Trump didn't mention the Cruz bill by name, but it wasn't difficult to connect the dots (though if that's what he was referencing, he greatly exaggerated the number of judges it would add). And the White House had said just the day before that Trump would not sign stand-alone legislation on keeping families together. “The president doesn’t just want to see a Band-Aid put on this,” White House press secretary Sarah Huckabee Sanders said Monday.

That could be changing. Members who met with Trump privately on Tuesday evening seemed to come away with the idea that he would sign a stand-alone bill or either of the broader House bills. That's anything but a certainty, though, given Trump's constant vacillations on issues like this. Trump said five days ago that he wouldn't sign a more-moderate House bill preferred by leadership, before the White House clarified that he would. Then earlier Tuesday he appeared to throw a wrench in the whole thing again by saying he would “make changes” to the House bills after he reviewed them with lawmakers. The last time we had an immigration debate, he pulled the plug on a bipartisan deal at the last moment — to the great consternation of negotiators like Sen. Lindsey O. Graham (R-S.C.). Anybody who says they know what Trump will do is lying or delusional.

And given Sanders's comments on Monday and Trump's comments about immigration judges in his speech Tuesday, it's anybody's guess what Trump will truly demand. It's not difficult to see him viewing a stand-alone bill as a rebuke of his zero-tolerance policy that resulted in family separations. And it would be a rebuke, in the truest sense of the word; GOP senators who want to end the practice insist Trump can do it unilaterally, but Trump has disagreed. They clearly think this is a bluff in the hope of obtaining concessions. Passing a stand-alone bill would essentially bring Trump's negotiating gambit to an end.

Republicans have chosen not to take this approach with DACA even though Congress could probably pass a stand-alone bill (and maybe even a veto-proof one) today, because nobody wants to run afoul of Trump. The result is that he's done pretty much the same thing again, except this time featuring tragic images and audio of children being separated from their parents at the border.

Do Republicans really want to see how far he'll go next time?