When Rishi Sunak speaks, the nation shrugs. There’s no coming back from that | Rafael Behr

Rishi Sunak is not a deep-cover agent of the Labour party, but politics might not look very different if the prime minister were on a secret mission to make life easier for Keir Starmer.

To achieve this feat, special operative Sunak would occupy positions expected of a Conservative leader, but in a way that minimised public enthusiasm and maximised division in his own party.

He would present himself as a unity candidate, then stagger around in the policy no man’s land between rival factions. He would be too soft to satisfy Brexit hardliners but still indulge populist bullies enough to alienate squeamish liberals. He would be close enough to David Cameron to elicit contempt from people who admire Nigel Farage, while aping Faragism enough to demoralise one nation Tories. With precision targeting, his messages would connect with no one.

For a masterclass in this technique, observe the flirtation with rupture from the European court of human rights. Sunak doesn’t want to be the prime minister who put Britain outside the purview of international law, but he also wants people to think he is prepared to do it if the ECHR obstructs his policy of deporting asylum-seekers to Rwanda. Last week, he told the Sun that “border security and controlling illegal migration is more important than our membership of any foreign court”.

The prime minister reinforces the neurotic nationalist concept of ECHR jurisdiction as an alien apparatus to obstruct sovereignty, but without quite committing to the action mandated by such a view. He tells his audience they are right to despise an institution that he is not actually leaving.

Sunak will not terminate UK membership of the ECHR, for at least two reasons.

First, the convention is woven into the text of the Good Friday agreement. Tidying up the mess that Boris Johnson’s Brexit deal made of Northern Ireland’s border arrangements and facilitating restoration of power-sharing at Stormont are the current prime minister’s only indisputable accomplishments. He is neither mad nor stupid, and he would have to be both to want to burn that legacy.

Second, even if he passed the derangement test, he wouldn’t have the time or political bandwidth to get it done in the current parliament. The furthest he could go would be a manifesto pledge that would be disowned by a substantial caucus of his MPs in an election he will lose. He is talking himself into a position he doesn’t really want and relying on the electorate to spare him the indignity of admitting that it was a bluff.

But everyone knows he’s bluffing, which makes the bluff worthless. Worse than worthless, because a transparent ploy is condescending to the voters. Even the people who want ECHR withdrawal turn their noses up at a prime minister who serves them their own opinions with a garnish of craven calculation.

Most people simply shrug. The prime minister says what he feels he has to say. Soon he will be gone.

But what if he also means it? Two opposing impulses can coexist in one mind. Sunak the spreadsheet-savvy administrator might not feel comfortable sabotaging Britain’s relations with other European democracies, while Sunak the reliably rightwing Conservative – a Brexit supporter when even Liz Truss was voting remain – might view judges in Strasbourg as enemies of sovereign border control.

Much railing against the ECHR has a hollow rattle – the slurp of still-thirsty Eurosceptics pushing their sticky straws around an empty campaign cup. The Strasbourg court is not an EU body, but the flavour of arguments about sovereignty is the same, and the appetite expresses an idea that defenders of a liberal world order should take seriously.

The core contention is that human rights law as it applies to refugees, as conceived in the aftermath of the second world war, is the relic of a bygone era. Patterns of migration in the 21st century demand policy remedies that the well-meaning architects of the ECHR, British lawyers prominent among them, could not have anticipated.

It is an enticing argument for anyone who wants to believe that Britain’s migration issues are best handled without the encumbrance of European institutions. But the opposite is true, given Britain’s geographic position and the fact that every frontier has two sides (unless the plan is North Korean-style reclusiveness).

Meanwhile, the spectacle of one of Europe’s oldest-established democracies repudiating its 20th-century treaties would gratify authoritarians who prefer a world where might is right and see liberalism as moral degeneracy leading to national decline.

Sunak doesn’t count himself in that company, which is why it would be interesting to know what he really thinks about Britain and the ECHR.

Everyone knows the tactical expedients: appeasing implacable Tory MPs; sending up rhetorical fireworks to divert the column of ex-Tory voters on their way to Reform UK. But panic in the face of impending defeat isn’t an argument.

If Sunak spelled out a detailed case for jettisoning human rights law, his opponents would be forced to respond. One nation Tories and the Labour frontbench would have to defend the subordination of British home secretaries to adjudications in Strasbourg. They would have to say why the 20th-century apparatus of law is still relevant, or set out plausible routes to a modernising upgrade. They would have to practise refuting arguments that are coming their way sooner or later.

Instead, the whole issue gets rolled up in the general trashing of the Conservative brand. The opposition gets to deflect hard questions about its own immigration stance by decrying incumbent incompetence. Pro-European opinion is comforted that the Brexit tide recedes automatically as the Tories are swept from power.

Something similar happened in the late 1990s, when John Major was hobbled by Eurosceptic rebellion. Liberal internationalists, basking in the long globalising boom, let their arguments atrophy through lack of exercise. The next Labour government will have no such luxury.

MPs on all sides say the mood in their constituencies feels more volatile than static poll ratings suggest, but they don’t see a way back for Sunak. He has been too diligent in stoking grievances exploited by his enemies and too deficient in the professionalism that was promised by his supporters. He is dismissed with a shrug, which is a powerful gesture but an ambiguous one.

Britain shrugging off a soiled old government doesn’t mean the opposition is a natural fit. There is growing consensus that it’s time for a change, but to what, nobody can say. Winning in a general shrug will cause a lot of trouble for Labour in government. That’s a problem the opposition is happy to have this side of an election, which looks hard to lose with Agent Sunak on their side.

• Rafael Behr is a Guardian columnist

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