For all his bluster, President Donald Trump has established a fairly consistent pattern of issuing bold threats for the enjoyment of his core supporters and then backing down when the moment of truth arrives or his advisers intervene.

There are exceptions, of course—like when he made good on his promise to exit the Paris climate agreement—but the trend is hard to ignore. Trump has backed down from threats to collapse Affordable Care Act markets by withholding subsidies, to unilaterally withdraw from NAFTA, to respond to North Korean taunting by launching a nuclear first strike, and to void the global powers agreement governing Iran’s nuclear program.

It’s not always clear who or what talked him down, but in general we have been left to assume that Trump caves because at least on some level he responds to reason. While Trump is reportedly obsessed with Barack Obama and consumed with the desire to demolish everything his predecessor built, he’s eased off almost every time—presumably because he knows the political consequences of such reckless sabotage would be severe.

But Trump is also profoundly ignorant and Id-driven, which means that if there is any restraint in the White House, we have to wonder whether it is Trump’s advisers—in the administration, on Capitol Hill, and elsewhere—who are holding him back from the brink.

For seven months, this unstable dynamic has been stalking our national policy, and no one but the president and his men—if even them—know if or when it will break down. In the past several days, Trump’s relationship with his advisers and lawmaking partners has reached a nadir. On Tuesday, at an unhinged rally in Phoenix, Arizona, Trump implied he would allow the government to shut down unless congressional appropriators agreed to fund construction of a wall along the Southern border. Now that the president has issued one of his largest and most baffling threats yet, we are about to learn whether Trump will break loose of his last constraints, and whether Republicans in Congress are prepared to take matters out of his hands when he does.