President Trump at the White House on Jan. 10 in Washington. (Jabin Botsford/The Washington Post)

PRESIDENT TRUMP spent the week sending ever-stronger signals that he would declare a national emergency and unilaterally direct funds to begin construction on a wall along the U.S.-Mexico border. On Friday, he backed off, saying that “what we’re not looking to do right now is national emergency,” and that he is “not going to do it so fast.” He should take the idea off the table for good. It’s wrong to use the threat that he might, at some future date, ignore Congress, as well as last November’s midterm election results as leverage in continuing negotiations.

An emergency declaration would set a dangerous precedent. Mr. Trump and future presidents would feel less constrained in asserting their right to act unilaterally, even on spending matters on which Congress’s authority should be paramount. The legal argument is that Mr. Trump would act according to powers Congress previously delegated to the president. Yet even if the courts accept this strained legal reasoning, the notion that there is a military emergency on the border demanding the reallocation of Pentagon funding would remain an absurd sham.

The move would represent a particularly obnoxious betrayal of the separation of powers, because Mr. Trump has pushed Congress hard, to the point of closing the government, for the money to build a wall and lawmakers have refused. It could hardly be clearer that legislators do not want taxpayer money to be spent in this way.

Some Republicans have raised concerns that future Democratic presidents would take Mr. Trump’s example and seek their own ways to maneuver around Congress’s wishes — to address climate change, perhaps — with their own adventurous interpretations of extant authorities delegated long ago to the executive branch. A future Democratic executive may not find as much legal grounding as Mr. Trump might now claim, but we also do not doubt the ingenuity of lawyers determined to take advantage of the thick web of emergency authorities delegated to the president.

There is another danger. If Mr. Trump helped establish the expectation that the invocation of emergency powers is often a partisan political exercise, then presidents would be met with more skepticism when they use those powers in more legitimate ways. This could harm efforts to unite the country, mobilize resources or obtain congressional cooperation in times of authentic crisis. Moreover, if Mr. Trump declares an emergency and loses his argument in the courts, judges might use the opportunity to constrict presidential emergency powers — for good or for ill.

As we argued Friday, Congress has likely delegated too much discretion to the executive branch to sidestep lawmakers’ powers during a presidentially declared emergency. Congress should review and rescind emergency powers that are outdated or too broad. But not every exercise of emergency authority would be unwarranted or unwanted.

Some members of Congress — both Republicans and Democrats — appear to believe that the only way to end the shutdown standoff is for Mr. Trump to declare an emergency, try to start building his wall, face an immediate court challenge and reopen the government as the lawyers argue. This is a depressing conclusion about the nation’s leaders. The blame lies squarely with the president, who has nixed seemingly every effort at compromise. But that does not change the fact that the only sound way out of the crisis is to craft a deal. With Mr. Trump saying there will be no emergency declaration for now, members of Congress should get on with it.