BRUSSELS — Britain and the European Union agreed on a Brexit deal Thursday, setting the stage for a fateful showdown in the British Parliament, where Prime Minister Boris Johnson faces an uphill struggle to marshal enough votes for his plan after three years of anguished, politically corrosive debate.
However, Johnson, who has yet to win a vote in Parliament as prime minister, may already be thinking beyond whether lawmakers approve this deal. Even if he loses, analysts say, he is likely to call for a general election in the coming weeks, hoping to win a mandate to do what Britain’s paralyzed political class has so far been unwilling to do: pull Britain out of the EU as swiftly as possible.
With Britain’s opposition Labour Party determined to reject the agreement and defeat Johnson at the polls, and with others hoping to force a second referendum that could reverse Brexit altogether, it all suggests a recipe for continued political upheaval.
“If Johnson gets the deal through Parliament, this is the end of the beginning,” said Timothy Garton Ash, a professor of European studies at Oxford University. “If he does not, Parliament with luck comes up with another way forward. It’s a fork in the road, but it’s hardly the end of the road.”
The deal ran into political headwinds almost immediately, when Northern Ireland’s influential Democratic Unionist Party refused to support it, saying it would cleave Northern Ireland from the United Kingdom and hurt its economy. The party’s rebellion deprived Johnson of his most obvious path to a majority.
Johnson, who called a special session of Parliament for Saturday, appears to be betting that he can cobble together enough votes from other lawmakers who are fed up with the endless wrangling over Brexit and may view this deal, however imperfect, as better than any alternative.
It is a breathtaking gamble by a buccaneering leader who has already upended Britain’s political establishment in his quest to take Britain out of the EU — shutting down Parliament for several weeks, purging rebels in his Conservative Party, and drawing a rare rebuke from Britain’s Supreme Court.
“This is Boris Johnson’s moment of maximum vulnerability,” said Anand Menon, a professor of European affairs at King’s College London. “He is vulnerable to criticism of the deal, and he is vulnerable to criticisms for not having left the EU.”
Johnson’s predecessor as prime minister, Theresa May, made a similar bet by calling an early election in 2017. She fared poorly and ended up in a minority government propped up by the Democratic Unionists, severely limiting her room to maneuver on Brexit.
On Thursday, Johnson basked in the approval of the 27 other EU leaders, who gathered in Brussels for a two-day summit meeting to endorse the deal. That was less surprising than it seemed, given the significant concessions that Britain made in days of frantic negotiations, mainly over how to treat Northern Ireland.
Under the terms of the agreement, Northern Ireland, which is part of the United Kingdom, would leave the EU’s single market and join a separate customs union with Britain. But it would remain closely aligned with a maze of European rules and regulations, allowing seamless trading to continue with Ireland, a member of the EU.
“I’m happy about the deal, but I’m sad about Brexit,” said the president of the European Commission, Jean-Claude Juncker, appearing alongside Johnson at a news conference.
An ebullient Johnson said: “This deal represents a very good deal both for the EU and for the UK And it’s a reasonable, fair outcome.”
In fact, it is at the extreme end of possible divorce settlements between Britain and the EU, with no promise of alignment between the two sides in commerce and trade, with the exception of Northern Ireland.
In terms of its potential negative impact on Britain’s economy, analysts said Johnson’s plan was not that different from a so-called no-deal Brexit, which he has repeatedly vowed to pursue if he could not reach an agreement.
The Johnson plan would reduce income per capita in Britain by an estimated 2.5 percent, relative to staying in the EU, according to UK in a Changing Europe, a research group that tracks Brexit issues. That compares to a 3.3 percent reduction if Britain left without any deal.
Leaving Europe without a deal, of course, would entail other potential dangers, including disruptions to trade, shortages of medicine, and unrest in Northern Ireland, not to mention a legacy of animosity with Europe.
The deal Johnson struck is also not radically different from a proposal Europe first made to Britain in early 2018, leaving Northern Ireland alone in the bloc’s customs union. May rejected that proposal, saying that it threatened the territorial integrity of the United Kingdom and that “no UK prime minister could ever agree to it.”
At the time, May was hemmed in by the Democratic Unionists, who exerted a strong influence over the hard-line, pro-Brexit faction of the Conservative Party. The party rejected any deal that distinguished Northern Ireland from the rest of the United Kingdom, which it saw as a first step toward Irish unification.
Johnson, an outspoken proponent of leaving the EU, somewhat diluted that influence, having earned the trust of hard-liners in his party. Yet, in winning that allegiance, he vowed to leave Europe by Oct. 31, even without a deal. That set off a rebellion in his own party and a vote by Parliament to force him to ask for an extension if he did not produce a deal.
Facing that prospect, Johnson proved to be an energetic negotiator, willing to make compromises where necessary. Britain moved closer to Europe’s insistence that there be no hard Irish border, offering a flurry of proposals about how to allow near-frictionless trade between the two jurisdictions.
But Johnson insisted that Northern Ireland remain legally part of a British customs union, which he viewed as critical to keeping the support of the DUP and hard-line Brexiteers. As his envoys haggled over terms in Brussels, Johnson met with a parade of unionists and other skeptics.
Hopes for a deal surged early this week, in part because there was little public dissent from the Democratic Unionists. A hard-line Brexit group in the Conservative Party, the European Research Group, voiced cautious support for Johnson’s plan. But as the language in the draft text became public, the Democratic Unionists quickly broke with Johnson.
If Johnson is defeated in a Parliament vote expected Saturday, he is likely to renew his call for a general election, arguing that he did everything he could to leave by Oct. 31 and that the voters should back him.