That President Trump is an almost compulsive liar, a man who is incurious about the world except to the extent that it can satisfy his crude immediate desires, has been obvious since he first appeared in public life as a real estate huckster in New York City. To some extent these were the qualities, or the defects, that won him the presidency. They made him relatable to millions of angry and bewildered Americans in his role as a reality TV star. They also made him a useful tool for more intelligent and strategically minded players, from Vladimir Putin to the Koch brothers, who have consistently used him to advance their own agendas and to weaken the American state at home and abroad.

One of the great questions arising from his success has always been whether he will pay for his lies, or whether it is only the US – and the rest of the world – which must do so. The outlines of an answer became rather clearer last week with the progress of special counsel Robert Mueller’s inquiry into Russian interference in the 2016 presidential election and the simultaneous inquiry by New York state prosecutors into the conduct of Mr Trump’s personal lawyer, Michael Cohen, the man who once said he would “take a bullet” for Mr Trump, who paid him $500,000 a year for this devotion.

As the prosecutors closed in Mr Cohen discovered that his first loyalty, after all, was to his family. Despite this enlightenment, he is facing more than four years in jail for multiple counts of tax evasion, bank fraud, and his role in coordinating with the Trump campaign two substantial payoffs to women who claim to have had affairs with the president. He also lied to Congress, as he now admits, over the negotiations Mr Trump was conducting, during his campaign, to open a Trump tower in Moscow. Mr Trump’s first campaign manager, Paul Manafort, is already in jail and faces as much as 10 years there. Now he’s accused by Mr Mueller of lying even after making a plea bargain earlier this autumn, over offences mostly concerned with the fortune he made as the recipient of lobbying payments from Ukrainian oligarchs.

In other news, the president has sacked his chief of staff, John Kelly, who will leave at the end of this month. That can’t be for lack of ideological zeal: General Kelly was an outspoken defender of the policy of separating children from their parents at the Mexican border. But he was also regarded by the outside world as a restraining adult influence, and that has never been associated with success at the president’s court. An earlier supposed grownup, Rex Tillerson, spoke out this week for the first time since he was fired as secretary of state. “So often … I would have to say to him, Mr President I understand what you want to do but you can’t do it that way. It violates the law.” Mr Trump responded by calling Mr Tillerson, the former president of Exxon Mobil, “dumb as a rock” and “lazy as hell”. His most recent diplomatic appointment is Heather Nauert, a former newsreader from Fox News, to be ambassador to the UN. She may know more of foreign affairs than he does.

All these aspects of his character have been on display for years. There is no more damning evidence of the president’s ignorance and dishonesty, or of his abiding faith in the stupidity of his audience, than his own public speeches and tweets. Now his inadequacies of character and intellect are beginning to damage even his own supporters in ways that cannot be explained away. His erratic and impulsive pursuit of a trade war with China has destabilised stock markets around the world. How long will his party continue to protect him? Republican appointees are a majority on the supreme court. Twenty Republican senators would have to vote against him for an impeachment in the Senate to succeed. The most chilling aspect of the present situation is that his survival may, in the last analysis, depend on politics rather than the laws that he once swore in his oath of office to uphold.