We are often told, including not least by Labour politicians, that the debate about Brexit is over. While it is suggested that there is scope for softening some of the harder edges of Boris Johnson's Brexit deal, the prospect of rejoining the single market or the customs union, let alone reopening the debate about EU membership, are said to be firmly off the agenda.
Nevertheless, seven years on from the referendum that paved the way for withdrawal, it seems that voters at least are having second thoughts.
YouGov has been tracking whether voters think the UK made the right or wrong decision in opting to leave the EU ever since the summer of 2016. Its polls show that doubts about the wisdom of Brexit, which never disappeared, have become widespread. The trend initially emerged when Brexit got its first rough ride in autumn 2021, when empty supermarket shelves and petrol pumps were blamed on a lack of lorry drivers from the EU. The doubts have gradually grown ever since. In the company's last half-dozen polls, on average just one in three (33%) have said that "in hindsight" the decision to leave was right. Well over half (55%) believe it was wrong.
Still, feeling a mistake might have been made does not necessarily translate into a wish to see a decision reversed. Voters might be reluctant to go through another divisive and potentially disruptive Brexit debate. Yet, in practice, they have also become increasingly inclined to say that, if given the chance, they would now vote to rejoin the EU.
Again, sentiment began to change in the autumn of 2021 - and swung further away from staying out of the EU as the economic outlook got gloomier in the summer and autumn of last year. On average, as many as 59% now say they would vote to rejoin the EU, while only 41% would back staying out. That said, as many as three-quarters of those who voted in 2016 would still vote the same way again. Many people's views about Brexit are firmly held.
However, whereas two years ago those who had voted remain were less likely than those who backed leave to say they would make the same choice, now the reverse is the case. I have calculated that, on average in the polls, just over four in five (81%) of those who voted remain now say they would vote to rejoin, whereas a little less than three-quarters (74%) of leave supporters say they would vote to stay out.
Still, the difference between these two figures looks too small to account fully for the 11-point swing away from Brexit that the polls have registered since 2016. Indeed, it is. What also matters - and has done so for some time - is the pattern of preferences among those who did not - or could not - vote seven years ago.
On average, just over half (51%) of those who did not vote in 2016 say they would vote now to rejoin the EU. Only one in seven (14%) would back staying out. (The remainder do not express a preference.) Evidently there are some people who now regret not having voted seven years ago. They are joined by a gradually growing group of those who were too young to vote in 2016 and who, having come of age, are overwhelmingly in favour of being inside the EU. Nearly four in five (78%) of those aged 18 to 24 say they would vote to rejoin the EU. The seven-year-old Brexit mandate is gradually being overtaken by demographic change.
We do not have to look far to ascertain why Brexit has become less popular. Most voters have not, of course, engaged in a careful analysis of the economic consequences of Brexit, difficult as they are to disentangle from the impact of Covid-19 and the war in Ukraine. However, the ever darkening economic clouds have helped cast a shadow over Brexit in their minds.
According to new polling by Redfield & Wilton for UK in a Changing Europe, as many as one in three (33%) of those who voted leave in 2016 believe that Britain's economy is weaker as a result of Brexit. And although half of this group say they would still vote to stay out of the EU, more than one in three (36%) would now back rejoining the EU.
Many leave voters are disappointed, too, about the perceived failure of Brexit to reduce overall levels of immigration. Strikingly, however, these voters are not particularly likely to have changed their minds about Brexit. Despite its prominence in the EU referendum campaign, immigration is not proving as crucial an issue as the economy in the current Brexit debate.
Inevitably, these findings raise questions about Labour's continued reluctance to challenge Brexit. While such a stance might have seemed sensible in the immediate wake of Boris Johnson's success in 2019, it might be thought questionable now that the decision to leave the EU is beginning to look so unpopular.
Labour's answer, at least, will be that the marginal seats the party needs to capture from the Conservatives to secure an overall majority voted more strongly for Brexit than did the country as a whole - by 56% to 44%. Consequently, it has to regain the support of the many leave voters who defected from the party over Brexit.
Indeed, the party has had some success in that endeavour. According to the latest polls, Labour support is 18 points higher than in 2019 among those who voted leave, compared with only six points among those who backed remain.
However, these figures exaggerate the extent to which Labour's support has changed since 2019. Those leave voters who have switched from Conservative to Labour are more likely than other leave supporters to have changed their minds about Brexit. The same is true of those leave voters who still voted Labour in 2019. Meanwhile, the party is well ahead among the many young voters who are pro-EU. As a result, as many as three-quarters of current Labour supporters are in favour of rejoining the EU, only marginally down on the equivalent figure of 82% in 2019.
There are, of course, plenty of other reasons why these voters are backing Labour, including not least the country's economic outlook. But while it might bite its tongue on Brexit for now, Labour needs to be aware it is heading for electoral success on the back of a predominantly pro-EU coalition of voters whom a Labour government might have to take care not to disappoint.
John Curtice is professor of politics at Strathclyde University, and senior research fellow at the National Centre for Social Research and The UK in a Changing Europe