Officials removed the British flag from the European Union Council in Belgium on January 31, 2020.Pool / Reuters

Remainers and leavers don’t exist in Britain anymore, a friend noted the other day. You can’t be in favor of remaining or leaving something you have already left. That ship has sailed. The new divide, he said, must surely be whether you are in favor of Britain rejoining the European Union or staying out.

This observation, made somewhat in jest, contains a number of truths. The first, most obviously, is that Brexit has happened—it is no longer a proposition but a living, breathing project. Fundamentally, now that Britain has left the EU, those seeking to lead the country must offer more than opposition to Brexit, but a program that seeks to make it work. This leads to the second truth, which is largely unacknowledged but no less real: The very fact of Brexit has turned many erstwhile pro-Remain members of Parliament into de facto Brexiteers—the more they succeed, the more they are able to help grow the economy, the more they improve conditions for ordinary people, the more they make their opponents’ case that Brexit was worth it. Only in Britons’ collective failure do the old remainers win, and actively seeking national failure is not a vote winner.

Tony Blair is, perhaps, the best example of this new reality. Once a leading figure in the Remain campaign, since Boris Johnson’s election victory Blair has argued that, while he still regrets the decision, “Brexit is happening, and our attitude now should be to strive to make the best of it.” His point was straightforward: Time to move on.

This change is subtle, but transformative. While it remains perfectly reasonable to reject this approach and seek voters’ permission to rejoin the EU, this is a new argument and harder to win. Rejoining the EU means another referendum and another negotiation. And, most importantly, it means rejoining a club that will be different from the one Britain voted to leave in 2016 (and on terms no one can be sure of). What was once the argument for stability and certainty is now the reverse.

This brings us to the third truth. By its very nature, Brexit will change Britain, creating new groups with vested interests tied to staying out of the EU. This is not because of a grand conspiracy, but because of the nature of politics—there is always a group that favors maintaining the status quo. Blair himself noted this point in his memoir, A Journey. Reflecting on the civil service, or what Donald Trump would call the deep state, Blair wrote, “The problem with them … was inertia. They tended to surrender, whether to vested interests, to the status quo or to the safest way to manage things—which all meant: to do nothing.”

Blair believed that, when in government, the political instinct pushing leaders toward indecision had to be constantly fought. He argued that avoiding decisions did not reduce political risk in the long run; it simply meant you did not get to choose the battles in which your wider war for votes was fought. Governments that reform things create dividing lines with their opponents that they want, not ones that emerge elsewhere in the vacuum of indecision.

With Brexit, if Johnson follows through with his plan to return what he has called “full legal autonomy” to Britain, he will suddenly have the power to create new dividing lines in a raft of new areas, from immigration and trade policy to fishing rights and agricultural subsidies, as well as those that were already in the government’s control, like prison sentencing, taxes, and public spending. As with all policy changes, there will be winners and losers: Domestic producers, for example, are forecast to benefit, while consumers are not; fishing communities might prosper, but at the cost, according to the EU’s negotiating mandate, of the wider British economy, which will have to pay a higher price when selling goods and services to the continent. The beneficiaries of these decisions might win big and have a vested interest in maintaining the new status quo, while the losers might barely notice at first, only paying the price over time. Such is the alchemy of politics that votes can be won by hitting large numbers of people a little bit for the great benefit of just a few.

All of this means that if Britain seeks to rejoin the EU in the future, it won’t just be a different EU it is joining, but a different Britain seeking a return. The rupture has happened and may prove too great to repair. Britain would have to not only accept the free movement of people and contributions to the EU budget, but also actively vote to resurrect these politically toxic realities of EU membership. It might also have to consider the euro and other facets of EU membership of which it had previously opted out.

The reality of the political cycle also means that any push to rejoin is likely to be some years away. The Conservative government has a commanding majority that will be hard for the opposition to overturn by 2024, the scheduled date of the next election. There is every chance that Johnson will be prime minister until close to 2030. Conventional wisdom suggests that for Labour to even stand a chance of winning, its next leader will have to seek votes from those who abandoned the party in 2019—many of whom voted for Brexit. Would they really vote for a party offering to reopen the question? Would any Labour leader really hang their leadership on this peg?

And yet, here a heavy caveat should be inserted. Four years ago, the Remain campaign was on course to romp to victory in the Brexit referendum, Donald Trump was not yet the Republican nominee for U.S. president, and France’s Emmanuel Macron was still François Hollande’s economy minister. The intervening four years have seen political parties and individual fortunes rise and fall across the Western world with remarkable speed as the impact of the financial crisis continues to be felt. To confidently predict the public mood in another four years’ time is brave at best.

No one can know whether Britain will rejoin or remain outside forever. No one can know if there will even be an EU to rejoin in 10 or 20 years, or what it will look like. The only thing that is certain today is that Brexit  has changed Britain and Europe for good and, in this regard, there really is no going back.

The risk for the Brexiteers is simple: that it all goes wrong. In taking back full control, Johnson has chosen the riskiest of the Brexits available to him, potentially jeopardizing the union with Scotland and Northern Ireland, who remain unhappy with the outcome. In Johnson’s view, Brexit without control is not Brexit at all. While this makes him master, it also comes with the chance of an economic fallout that will undermine the very project he seeks to bring about. The flip side of choosing the political battles you want to fight is that you must own both their victories and their defeats.

We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.