An angry and disturbingly pumped-up Boris Johnson’s response to the court in the recalled House of Commons tonight was an act of total contempt – for the courts, for parliament and ultimately for public and political decency. For the time being, Johnson still retains much of the formal power of the prime minister. But the role’s inner power, its moral authority, the holder’s ability to govern and his meaningful capacity to represent the country are practically shot. There is nothing tragic about this for Johnson personally. There is everything tragic for the country that never asked for him to become its leader.

He can’t blame the judges, because he does not dare. He likes to blame MPs, because they are an easy target. But the real blame lies with himself and the Tory hard leavers.

On Tuesday, in the immediate aftermath of the supreme court’s unanimous finding that Johnson’s attempt to silence parliament was unlawful and void, it was still just possible to suppose that the prime minister’s instant reaction in New York was merely foolish and off-the-cuff. While claiming to respect the court, Johnson and his lieutenants had gone into instant denial. Johnson announced that he “disagreed profoundly” with the ruling, as if that disagreement was in any way relevant. Meanwhile in London, Downing Street charged the justices with extending their reach into political matters, and Jacob Rees-Mogg was alleged to have described the ruling as a “constitutional coup”.

Perhaps, after sleeping on the matter, and with the prospect of a resumed parliamentary session in front of them, there was a possibility that the Johnson government would adopt a humbler and more contrite tone in the light of day today. Not a bit of it. First, with Johnson still in the air over the Atlantic, Michael Gove went on a media round and announced that the government had done nothing wrong in suspending parliament in the way that the court had ruled against. Then the attorney general, Geoffrey Cox, told the reassembled MPs that the government had acted in good faith, refused to rule out a further prorogation, and then lost it altogether, dismissing parliament as “dead”, “a disgrace” and possessing “no moral right to sit”.

These were merely the warm-up acts for Johnson’s own eventual appearance in the Commons this evening. But they had already pointed unerringly to the strategy that the prime minister was to adopt and which, it was now clear, he had intended to adopt from the very start when he spoke in New York. That strategy was that this is now a naked political fight to the death with the opposition and with the unbelievers. He is not interested in any of the issues on which the judges ruled. All that matters to him is to wade through chaos to Brexit. The twin objectives of the Johnson government when it took office after the ousting of Theresa May – Brexit by the end of October and a general election fought on a “people versus the elites” platform – remain utterly unchanged by the supreme court ruling.

Johnson’s two-month premiership has been based on an audacious and slightly crazy plan. It still is based on it today, even after Tuesday’s humiliation. That plan is the overriding need, as the Tory right sees it, to deliver Brexit after three years, and in so doing marginalise the Brexit party in a general election. The as yet insuperable problem with the plan is that it is fuelled wholly by the kind of bravado and pomposity that Johnson displayed this evening. There is a hung parliament, which means the Johnson Conservatives cannot get their own way without compromises they are not prepared to make. And there is the rule of law, which means they cannot ignore the constitution and the courts.

To Johnson, these are merely distractions. His objective remains to achieve his two goals by hook or by crook, come what may. If parliament supports him, fine. But if parliament opposes him, he will simply bank the defeat and use it to accuse MPs of being determined to frustrate the 2016 vote. Similarly, if the law supports him, that is fine too. But if it doesn’t – and this week it has not – then this too becomes part of the narrative that sees Johnson as the tribune of the leave majority and the courts as part of the resentful, threatened remain minority of establishment bad losers. There are loud echoes here of Donald Trump’s response to this week’s early moves to impeach him.

It may have been tempting, especially for liberals, to imagine that an event like an impeachment process or the supreme court ruling will be generally seen as disturbing enough to change the public mood. Maybe it should be. But it might be wise not to bet the mortgage on that. Most of the public say that they support the rule of law. Most, to judge by the instant polling after this week’s ruling, think it is bad that Johnson broke the law. But that does not mean that they will necessarily turn against Johnson in decisive numbers on issues such as Brexit or parliament’s delay in implementing it.

Modern Britain has undoubtedly become a much more law-respecting society today than it was in the past. This is an enormous change from the mid 20th century. In the 1970s, for instance, belief in the rule of law was far from universal, notably in industrial relations, where several unions boycotted the industrial relations court set up by the Heath government.

But the vestigial belief that the law should keep a certain distance from politics is deep-seated. The trade union movement spent most of its existence believing that the law had no place in industrial relations. Media interests, old and new, often talk in similar terms about the news business. Jonathan Sumption, a former supreme court justice, gave his Reith lectures this year on these delicate boundaries. So when Downing Street says the courts are overreaching themselves, they are not playing to an empty house.

Liberal Tories may be deceiving themselves in another way. They continue to believe that Johnson’s aim is really to make a deal with the European Union at the 11th hour. It would be the rational thing to do, they say, and in their own terms they are entirely right. Ken Clarke said this today. David Cameron said much the same in interviews last week. Johnson repeated it last night. All this, though, mistakes the fact that Johnson is rounding the point of no-return. Like Macbeth in blood, he is stepped so far in recklessness that there is no going back to the kind of compromises and trade-offs that even Johnson voted for earlier in the year.

Sooner or later, all this will be put to a general election. When that happens, it is clear that Johnson intends to focus his campaign against the pro-European establishment of liberal Britain. That was his aim in July, and it is still his aim now. He is calculating, in other words, that this week’s defeat in the courts can be leveraged into a much bigger victory at the polls. To be savaged by the judges is indeed humiliating. But if it helps to fire up enough leave voters in enough places to give Johnson some sort of electoral victory under Britain’s first-past-the-post electoral system, and with the anti-Tory opposition deeply split, it will all be deemed to have been thoroughly worth it.

• Martin Kettle is a Guardian columnist