King Charles is in America this week on a state visit, trying to repair what Britons used to call the “special relationship”. But most have already made up their minds about America under Donald Trump. Last year, 56% of Britons said they distrusted the US – and that was before the US president threatened a NATO partner, described the Royal Navy’s aircraft carriers as toys, and considered withdrawing recognition of UK sovereignty over the Falkland Islands.

Public debate has shifted to how Britain can shield itself from external coercion, whether from Russia, China or now the US. That has naturally revived talk of whether Britain should rejoin the EU.

The speed at which the conversation has moved is remarkable. A year ago, public discussion about the damaging consequences of Brexit was virtually taboo across the UK establishment, resisted by all major political parties and officials for fear of reopening political wounds.

Not so today: the Prime Minister and Chancellor have both spoken at length about the damage of Brexit. The civil servant who led the Brexit Department during the withdrawal negotiations wrote last week that Brexit has delivered none of its claimed benefits and called for a debate on reversing it. Talk of rejoining is now literally front-page news.

Polls show public opinion shifting in this direction. According to a survey conducted for Best for Britain, a pro-EU campaign group, 53% of voters would now support rejoining, including 25% of Leave voters, with only 24% strongly opposed. Another poll found that 58% of voters think Brexit was a mistake, while only 30% think it was the right decision. Simple demographics suggest those trends will become more pronounced as many of the elderly voters – who disproportionately voted for Leave – will have died since 2016, while 83% of young voters support rejoining.

Turning those numbers into a political mandate will not be straightforward, however. None of the major parties has come close to advocating rejoining, and two – the Conservatives and Nigel Farage’s Reform Party – are fiercely opposed. The most pro-European party, the Liberal Democrats, will only say it supports rejoining the Customs Union and single market.

Labour won’t go even this far, continuing to stick by its 2024 manifesto red lines: ruling out rejoining the Customs Union or single market and rejecting a return to free movement. Instead it proposes aligning UK regulations with the EU in the hope of securing enhanced single market access.

Could the political landscape change before the next general election, not due until 2029? That is what British pro-Europeans hope. So far, Starmer’s much-vaunted EU reset has delivered only modest gains. At a summit later this year, the two sides are expected to announce deals on food standards and carbon trading. The UK is already rejoining the Erasmus student exchange programme, but a youth mobility deal is stalled on whether EU students should pay domestic fees at UK universities – a price the British government considers much too high.

Moving beyond even this limited agenda looks difficult. The British government dreams of a Swiss-style relationship built through further sectoral deals. But Brussels is adamant that such cherry-picking is not on offer. And even where access is granted, the price for a non-member might be prohibitively high – as Britain discovered when it rejected the terms offered to join the EU’s joint defence procurement programme last year.

Besides, arrangements that would leave Britain as a rule-taker – including Customs Union or single market membership – were firmly rejected during the Brexit negotiations. Polls show that these options are less popular than rejoining the EU outright: proof that the public understands the real choice is binary.

The question is whether the political class will grasp this reality before the next election. Much may depend on the actions of Donald Trump, Vladimir Putin and Xi Jinping. One thing seems certain: the costs of Brexit – which a rigorous analysis last year calculated may already amount to as much as 8% of GDP – are likely to grow as the EU takes steps to boost its resilience and deepen its autonomy in technology, energy, defence and finance. With the EU contemplating protectionist measures such as Made in Europe, Britain may face new barriers to trade.

At the same time, as Europeans search for new collective defence arrangements to compensate for a possible US withdrawal from NATO, the EU is likely to take a greater role in continental security – at least in future procurement, perhaps financed by common borrowing, if not in the operationalisation of its Article 42.7 mutual defence clause. Britain will of course continue to play an important role under any circumstances via ad hoc coalitions of the willing, but many will regard that as a poor substitute for a seat at the EU table.

The critical moment will come if and when Sir Keir Starmer is removed as prime minister – perhaps even later this year. Will a new Labour leader in urgent need of a growth strategy and a new narrative adopt a manifesto commitment to rejoin the EU? Many think that possible, even likely, given that is what 83% of Labour voters say they want. And if other left-leaning parties – along with the Welsh and Scottish nationalists – also embrace rejoin, it is not inconceivable that the next election could deliver a parliamentary majority in favour.

That would still leave the small matter of negotiating a new accession treaty and, perhaps, securing public consent in a referendum. While many EU leaders have talked about their hopes for a UK return, Brussels is sure to drive a hard bargain. There will be politically difficult trade-offs to confront, not least on cost, free movement, and euro membership. None of this will be easy. But for the first time in a decade, it doesn’t look completely far-fetched.