Protesters rally in support of the Deferred Action for Childhood Arrivals program in Los Angeles on Sept. 1. (Frederic J. Brown/AFP/Getty Images)

THE TROUBLE with forging a deal to allow “dreamers” to remain legally in this country isn’t that Democrats and Republicans can’t agree with each other. It’s that President Trump can’t agree with himself.

At various times, Mr. Trump has suggested that dreamers should, and should not, be allowed to stay in the United States. He has said that a massively expensive border wall should, and should not, be part of any compromise on dreamers. He has repeatedly expressed compassion for dreamers, and now, by connecting their prospects to a kitchen-sink set of hard-line demands, made clear he sees them as no more than a bargaining chip to advance the Republican Party’s sweeping nativist agenda.

The president’s shape-shifting on the dreamers, as on so many other issues, is a symptom of his indifference to policy and absent moral compass. Which is why Congress should step in and resolve the plight of these nearly 700,000 young immigrants, most of them brought to this country illegally by their parents as children, whose protection from the threat of deportation will lapse next year owing to Mr. Trump’s decision to rescind President Barack Obama’s Deferred Action for Childhood Arrivals program.

Congress need not be captive to the White House’s laundry list of demands, released Sunday, to which hard-liners would attach — and thereby doom — legislation to legalize the dreamers’ status in the United States. Those demands include funding for a border wall; a constriction of long-standing rules governing legal immigration; a crackdown on minors from Central America who enter the country illegally; tools to prevent employers from hiring undocumented immigrants; and other priorities of Republican xenophobes who see political peril and cultural decay in the specter of an increasingly diverse United States.

In fact, there is political and moral logic in pushing ahead with a “clean” bill to deal with the dreamers.

The political logic is there is no immigration-related issue on which Americans have reached so broad a consensus as they have on conferring legal status on the dreamers, to shield them from the threat of deportation and allow them to study, work and lead normal lives. In polls, a large majority of Americans agree on this; in Congress, all Democrats and many Republicans also agree. So why gum it up with more contentious immigration debates?

The moral logic is just as clear-cut. Dreamers, most of them in their teens, 20s and early 30s, have grown up in the United States, gone to American schools and colleges, speak English and, having qualified for the DACA program in the first place, have clean records. Many work; some own cars, homes and businesses. They are neighbors, friends, classmates and colleagues; they are Americans in all but the most technical sense. It would be preposterous at this point to threaten them with deportation, let alone to expel them en masse.

That’s why it’s also politically and morally illogical, and untenable, to freight their cause with every other immigration issue. This one issue really can stand alone, and be fixed — even by a Congress that seems incapable of fixing anything else.