Henry Nicholls / Reuters

Such is its devilish complexity, Brexit is often portrayed as a game of 3-D chess, understandable only to the grandest of grand masters. Yet in reality it is far simpler: a tedious game of political tic-tac-toe (or noughts and crosses, for our British readers) in which each side is forever countering the previous move by its opponent but unable to ever triumph. The winner is, then, not a master strategist, but simply the one who is last to make a mistake.

This is how best to understand the series of seismic but impenetrable battles being waged between Prime Minister Boris Johnson’s government and his opponents in Westminster this week: battles that are not primarily about what they claim—whether for this motion or that amendment—but rather part of a much larger but simpler game in which each side is trying to ensure that it is not outmaneuvered by the other in a way that will make victory or defeat inevitable.

The problem is that, in Brexit, the two sides have thus far been evenly matched and always able to extend the game to avoid a conclusion. With no majority for any party in Parliament, the government’s every move can be countered by the opposition—one step forward, one step back. Yet the opposition, united in what it does not want, has proved unable to agree on what it does want, and therefore cannot outmaneuver the government in return. The opposition does not want Britain to leave the European Union without a deal, so it can block Johnson’s moves to force one, yet it is not united in wanting a second Brexit referendum, so cannot force one. The result: an endless charade of marking X’s and O’s without any chance of a breakthrough.

That is, until now. Over the past week, something significant has happened, which has potentially changed the game. This has not been immediately visible, and will continue to be obscured by the political theater of parliamentary battles over the next week or so. But for the first time in three years, the British government, at least on paper, appears to have assembled a majority in Parliament for a divorce deal with the EU. This may yet fall apart—perhaps as early as today—but it is a big moment all the same.

The development came last week, when Johnson struck a deal with Brussels, paving the way for a hard Brexit—allowing a much looser economic and political relationship with the EU than former Prime Minister Theresa May had envisaged—despite it not having the support of his parliamentary ally, Northern Ireland’s Democratic Unionist Party. This decision did two important things: First, it united the Conservative Party, including the majority of members of Parliament kicked out of the party by Johnson for voting against him. Second, it won the support of a number of Brexit-supporting opposition MPs. Together, this meant, according to publicly declared intentions, that the government for the first time had a (slim) majority for Brexit (something May never got close to).

This reality was obscured by a move over the weekend to delay ratification of the deal until Parliament had a chance to scrutinize legislation (which is required to integrate the proposed divorce treaty with the EU into domestic British law). In other words, it postponed the day of reckoning when MPs either grant or do not grant consent. A similar tactic will be used by lawmakers again today—seeking to extend the length of time needed to debate the proposed divorce treaty. While these maneuvers do create more time for debate and analysis in Parliament, they also function as a play for time in the hopes of drawing out a mistake from Johnson.

The delaying tactic worked because enough MPs from Johnson’s own side remained sufficiently worried about the prospect of an accidental no-deal Brexit to vote against the government. Johnson’s closest advisers are worried that the same thing will happen again today. If it does, Johnson’s “do or die” commitment to Brexit by October 31 looks in trouble, which is the whole point of the opposition’s move.

Yet a significant number of the MPs who are happy with delay now say they are also willing to support his Brexit deal. In other words, despite being willing to slow the process, they now also appear willing to fall in line and back Johnson.

This is a potentially seismic turning point in the Brexit drama, so long as the government can persuade all those MPs who have professed their support to stick with it. As long as the numbers stay as they are, the game of tic-tac-toe now looks stacked—the opposition’s moves are only delaying tactics unless it finds a way of splitting the majority in favor of Brexit. It either keeps delaying Brexit and risks an election in which Johnson is well placed, with a united party behind him and a deal to present to the public, or it eventually sees its opposition worn down and Brexit delivered.

The game is not over—Johnson’s coalition is fragile and he could yet make a fatal mistake under pressure. There are concerns, for example, about the prospect of checks on goods moving from Northern Ireland to the rest of the United Kingdom, a symbolic border between two parts of the same country, which may yet blow up into a full-blown crisis for the government.

A number of supersize asterisks also need to be added, marked up in bold, underlined, and highlighted for good measure. First of all, it remains a big if whether the Labour MPs who have broken from their party’s opposition to Johnson’s deal and who are now crucial to Johnson’s majority will stick with him. Second, even now the opposition appears to have the numbers to frustrate the government on timing—and even, perhaps, on some of the substance of Johnson’s deal. Clever parliamentary tactics this week and next are likely to be deployed to make life difficult for the prime minister, tempting him into making a mistake. Amendments could be proposed—such as protections for workers’ rights or a possible customs union with the EU—which could cause Johnson and his government serious disquiet if they pass, by making it harder for his own MPs to support the deal. The Conservative Party, not known for its discipline over the issue of Europe, will have to remain unified.

The biggest asterisk of all, however, is long-term. Once the U.K. is out of the EU, the country’s political world changes irreversibly. Opposition parties must decide if they accept the new constitutional reality or not. Johnson, meanwhile, will go into the next election as the man who delivered Brexit. And there is still no majority for what Britain’s future relationship with Europe looks like—the Brexit deal Johnson assembled sets only the terms for Britain’s withdrawal from the bloc. Labour MPs prefer a close relationship with Brussels based on equal rights for workers and minimum European standards, while Johnson’s Tory backbenchers want a loose relationship in which Britain is freer to compete economically.

Until Johnson has a comfortable majority of his own, the game of tic-tac-toe will continue even after Brexit—a never-ending back-and-forth.

Even if Britain leaves the EU this month, on October 31 as scheduled, it would soon be in its next crisis, having to decide whether it wants to extend the “transition period” created in the exit deal—a kind of bridge between full EU membership and whatever future relationship is agreed on. Experts say there is little to no chance that the U.K. could agree on a free-trade deal with Brussels before the end of 2020, when the transition period is supposed to expire. This means Johnson could be forced to apply for an extension of either a year or two next summer—something his own MPs will abhor. Through it all, the prime minister will have to determine what kind of trade deal to negotiate with the EU.

For Britain, the end game of stage one might—might—be drawing tentatively (and perhaps lengthily) to a close. Yet even if Johnson can keep his delicate majority together, the longer battle is only just beginning. Welcome to the never-ending Brexit.

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