JUST as a frog in warming water cannot sense its own destruction, America is said to be increasingly inured to the harm President Donald Trump is doing it. The scandals and affronts are too many and too various to keep in mind—and also too confusing. It is hard to tell a toxic tweet from a major corruption scandal from an attack on the constitution. Just as the frog begins to suspect there is something seriously amiss, along comes a reason to think his pond is just a bit warmer than normal.

An extravagant legal row this week suggests there may be little time left for complacency. In a leaked 20-page letter written to Robert Mueller, the special counsel who is, among other things, investigating Mr Trump for possible obstruction of justice, John Dowd and Jay Sekulow, both lawyers for the president at the time, made a series of breathtaking claims for the powers of his office. It amounted to an argument last heard from Richard Nixon: that the president is above the law. Yet the Republicans who control Congress, and are therefore chiefly responsible for checking the president’s ambitions, mostly played along. To extend the amphibian analogy, this illustrates a combination of executive activism and congressional dysfunction that has been simmering for decades. It has left America more vulnerable to a rogue president than at any time since Watergate.

The president’s lawyers made three broad claims for their client. They said he was not obliged to submit to Mr Mueller’s request for an interview, on the basis that he had already provided the investigator with sufficient documentary evidence. That is surely wrong. The special counsel is believed to want to ask Mr Trump why he sacked James Comey. If he did so because he was dissatisfied with the FBI director’s performance, Mr Trump acted within his power. But if he did so because Mr Comey was pursuing an investigation into Mr Trump’s associates’ ties to Russia, he abused it. As the president has offered both explanations, Mr Mueller reasonably wants oral clarification from him on the matter. And in a rule-of-law state, Mr Trump has no political grounds to refuse that request or the subpoena the special counsel could enforce it with.

The lawyers also claimed that Mr Trump was in any event incapable of obstructing the course of justice because, as America’s chief law enforcement officer, he could do whatever he liked with Mr Comey’s investigation. That is a more ticklish argument: the obstruction laws are complicated and the ambit of presidential power vast. Yet, again, it rests on the question of Mr Trump’s motivation. The president is entitled to exercise his constitutional powers, but not for corrupt purposes, which is why Mr Mueller wants to ask Mr Trump what his purposes were.

Uneasy lies the head

In case the special counsel had the temerity to press his request, Mr Trump’s lawyers raised a third spectre. The president “could, if he wished, terminate the inquiry, or even exercise his power to pardon if he so desired.” Two days after the letter was published, Mr Trump echoed that point on Twitter. “As has been stated by numerous legal scholars, I have the absolute right to PARDON myself, but why would I do that when I have done nothing wrong?”

It is unclear whether he really does have that power. No president has pardoned himself before. And the notion that one could seems to jar with the view, held by most legal scholars, that the president cannot be indicted in office. The nearest thing to an authority on the matter, though it has no legal force, is an opinion written in 1974 in which a justice department lawyer argued that the president did not have the power to self-pardon. Nixon resigned three days later.

Yet this was ultimately because Congress, belatedly but resoundingly, had turned on him. And that looks far less likely these days—even in the event that Mr Trump defied a subpoena from Mr Mueller or absolved himself of a crime. Freed by his decision not to seek re-election, Paul Ryan, the Speaker of the House of Representatives, did muster the courage to say he was not for presidential self-pardoning. His counterpart in the Senate, Mitch McConnell, kept silent. Meanwhile he refuses to allow a vote on draft legislation intended to protect the Mueller investigation from the attack Mr Trump has threatened. If Congress will not fulfil its duty to check monarchical ambitions, America can expect more errant presidents.

How far Mr Trump may be willing to test Congress’s acquiescence is one of the most important questions of his presidency. It is possible to be optimistic. The president has a careerlong habit of making blustery threats that he does not follow through on, often in an effort to secure only modest advantages (as Kim Jong Un may be about to discover in Singapore). Mr Trump’s former lawyers, having claimed vast powers for the president in a bid to spare him an interview with Mr Mueller, seem to have employed the same tactic. Legal scholars noted that the shabby quality of their legal argument also had a distinctly Trumpy feel to it. The lawyers argued that Mr Trump’s meddling with the FBI did not break a particular statute on obstruction. Yet they failed to mention a far more pertinent statute in Article I of the constitution.

A more pessimistic view is that, even if Mr Mueller were to call Mr Trump’s bluff, the stakes are too high for the president to fold as he usually would. The presidency is not a deal he can easily walk away from. That this might even be a consideration presupposes, of course, that Mr Mueller has him on the hook for a serious offence. He may not. Though, it must be said, that is not the impression Mr Trump and his lawyers are giving.