Even though he is already noted for being at best erratic and at worst eccentric, US President Donald Trump’s most recent comments and conduct have caused considerable alarm at home and abroad.
First there was his preposterous demand to buy Greenland from Denmark. When he was predictably rebuffed, he cancelled a state visit to Denmark and called its female prime minister "nasty", a word he frequently applies to women.
Then there was his enthusiastic endorsement on Twitter of an obscure radio host’s comments that “the Jewish people in Israel love him like he’s the King of Israel. They love him like he’s the second coming of God.” Never mind that the concept is anathema to Judaism.
In the same spirit, when defending his trade war, Mr Trump declared he was the “chosen one” in tackling China, appealing to the heavens for confirmation with upturned eyes and outstretched hands. He later insisted he had only been joking but he isn't noted for having a keen sense of humour. Certainly no one was left laughing.
Mr Trump similarly likes to repeatedly joke about holding power beyond the constitutional limit of eight years, as he did yet again last week. But these frequent quips are obviously intended to prepare the public for that possibility – and he is plainly at least half-serious about it.
But perhaps the most troubling of his comments over the last few days were the most anti-Semitic made by any prominent American leader, let alone a president, in many decades. The president is reportedly outraged that many Jewish Americans remain strongly opposed to him, despite his pandering to the Israeli annexationist right.
He declared that Jewish Americans who vote for Democrats (at least 70 per cent routinely do) are showing "great disloyalty” by not supporting him. The next day he unconvincingly claimed he meant they were being “very disloyal to Israel”.
Republicans and Democrats joined a chorus of immediate condemnation. As David Harris, the chief executive of the usually politically cautious American Jewish Committee, said: “His assessment of…‘loyalty’ based on their party preference is inappropriate, unwelcome and downright dangerous.” Although Mr Trump upbraided reporters that this is only "anti-Semitic in your head", in fact the charge of disloyalty is the essence of modern western anti-Semitism.
Mr Trump’s behaviour has fuelled renewed demands for his impeachment, a move key Democratic leaders still regard as highly risky as the Republican-controlled Senate would most likely acquit him.
The even more fanciful idea that Mr Trump should be removed by his own administration under the provisions of the 25th Amendment has also reappeared. The amendment was intended to deal with the consequences of a president in office dying, resigning or being incapacitated by illness. But when the sitting president suggests he has messianic status, that notion predictably resurfaced, with the hashtag #25thAmendmentNow trending on Twitter.
Mr Trump's outlandish outbursts could be prompted by a growing realisation that his plan to run primarily on the strength of the economy is deeply threatened. Manufacturing is down badly and growth has returned to the Obama-era levels he ridiculed as terrible.
It is now evident that, yet again, a massive tax cut has not led to either a wave of capital investments or a major surge of growth. It has just meant a transfer of wealth to the already very-rich and has bloated the budget deficit alarmingly.
In response, Mr Trump broke new ground in American central-command economics with an inexplicable order that US companies disengage from China. He lacks the authority – but not the arrogance – for this heretofore unimaginable commandment.
Republican and business leaders were clearly aghast at this de facto socialism from a supposedly conservative administration but were at a loss as to how to respond.
Mr Trump has been working hard to set up the Federal Reserve Bank and its chairman as the fall guy if the economy continues to drift towards a recession.
On Friday, he launched what is easily the most vicious attack by any US president on one of his own appointees, tweeting: “My only question is, who is our bigger enemy, [Federal Reserve chairman] Jay Powell or [China’s] Chairman Xi [Jinping]?” – effectively accusing him of being both treasonous and an enemy of the state.
Yet with his intensifying trade war with China almost universally identified as the main cause of economic gloom, Mr Trump's prospects for re-election are visibly and rapidly dimming.
He might value unpredictability but investors never do. And his own erratic comments seemed to fuel a major stock market decline on Friday.
Nonetheless, calls for impeachment, let alone invoking the 25th Amendment, are hollow.
The American constitutional structure assumed that presidents would embody certain minimal standards of public-spirited duty, competence and propriety. If an inappropriate individual gains the position, Congress is empowered to implement the needed correctives.
But the Constitution was drafted before party loyalties developed. It was assumed lawmakers would jealously protect the institutional prerogatives of Congress, not allegiance to a presidential party leader.
Consequently, there is now no meaningful check on a president who retains significant support in the Senate, no matter how inappropriate and disturbing their behaviour might be.
Still, this week dramatically illustrated how easily once seemingly immutable norms and principles can be shredded by a president no longer restrained by anyone – even himself.
Hussein Ibish is a senior resident scholar at the Arab Gulf States Institute in Washington