It feels quaint – maybe a bit absurd – to remark the fact that Donald Trump has no constitutionally moral justification for his demand that Congress fund the building of a wall on the Mexican border. Such an argument feels absurd when made against this president. Yet it should not be insignificant to Congress.

The president ran on a promise to build a wall “paid for by Mexico”. No majority of Americans has ever voted to support that idea. But that idea is not the notion that is now shutting down the government. A wall paid for by taxpayers is. That wall certainly was a central issue in the 2018 midterm elections. Overwhelmingly, the public rejected it as well. Thus has the president earned public support for neither version of his Mexican wall. Yet he is using his veto power to demand that Americans pay for a wall before he will allow the government to reopen.

The American constitution does not contemplate such presidential unilateralism, at least unsupported by the public’s will or the constitution. Perhaps the most salient historical parallel is President Andrew Johnson’s insistence that he had the constitutional right to control (and effectively stop) reconstruction after the civil war. Like Trump, Johnson insisted on his power; like Trump, he campaigned across the country to rally the nation to his view; like Trump, his view was overwhelmingly rejected at the polls; like Trump, nevertheless, he persisted – until a Congress, exhausted by his recalcitrance, impeached him and came within a single vote of conviction.

The partisan gridlock of Washington has already sorely tested the framers' system of checks and balances

History has taught that Johnson had the better argument constitutionally, at least on the narrow question that ultimately determined his fate – whether the president has an unconstrained right to fire executive officers. But no reading of our constitution would ever uphold the view that a president can morally stop the functioning of government, to insist upon a program unsupported by the public or unrequired by the constitution.

Of all the constitutional norms that this president has upset, this, ultimately, may be the most significant. And it is this innovation that the Republicans especially should check. For do they now concur in the precedent that a president has the constitutional authority to insist upon whatever policy he likes, regardless of its support in the public? If a Democrat were elected on the promise to establish single-payer healthcare, does she then have the moral authority to shut down the government until Congress nationalizes the insurance industry? Or directly regulates pharmaceuticals? If she were elected on the promise to address climate change, can she stop the ordinary functioning of government until Congress passes a carbon tax?

The partisan gridlock of Washington has already sorely tested the framers’ system of checks and balances. We are, already, in the words of Francis Fukuyama, a veto-ocracy. Gone is the norm of governance, where both sides recognize their duty to come to terms with the other. Petulance is confused with principle. And the institutions of this constitutional democracy are critically weakened in the mix.

No doubt, the idea of a president elected by the people exercising the people’s will against a recalcitrant Congress has longstanding pedigree. But this president does not act for the people. He does not act to defend the constitution. He acts to avoid, as he acknowledged to Senator Chuck Schumer, “seeming foolish”.

Yet Trump is certainly not the fool in this tragedy. The fools are they who enable this constitutional immorality. Those fools are the Senate Republicans, who have placed party over country, and President Trump over the Republican party.