After unexpected political charisma and cunning propelled him to another term as Britain’s prime minister, David Cameron will now need every ounce of those skills to avoid going down in history with an altogether different title: founding father of Little England.

A result that maintained the status quo at 10 Downing Street masked the dramatic transformations roiling Britain, ones that threaten to leave this country more isolated than at any time in its modern history.

Thursday’s election may become just the first in a trilogy of rapid-fire votes that set this island adrift from Europe, divide it in half along ancient lines of national identity and ultimately leave behind a rump state of ever-diminishing value to its American allies.

“Yesterday was V-E Day, when the United Kingdom was celebrating its finest hour. Seventy years later, it could be contemplating the beginning of its end in its current form,” said David Torrance, a British political analyst and author. “The next five years will be a twin debate about two unions — the European Union and the United Kingdom.”

The questions of whether Britain stays whole and whether it remains in Europe are deeply entangled, with the outcome of one expected to heavily influence the other.

If Britain leaves Europe despite notably pro-European sentiment in Scotland, the chances of Scotland’s newly empowered nationalists leading another drive for independence would instantly rise — despite a promise that last year’s failed bid was a “once-in-a-generation” event.

That’s one reason that Europe is likely to be settled first. Cameron’s reelection fired the starting gun on what is sure to be an emotional and high-stakes debate over Britain’s future in the E.U.

Cameron promised a referendum on the matter by the end of 2017, but some are pushing for the vote to come far sooner so that uncertainty doesn’t hang over Britain’s economic and political fortunes for the next 2 1 /2 years.

Polls suggest that if the vote were held today, Britain would choose to stay in the E.U. But the energized voices for “out” are gearing up for the fight, in the belief that the country could better manage itself without meddling from Brussels.

Opponents of an exit say it could be catastrophic, leading to an exodus of jobs and a muffling of Britain’s voice both in Europe and beyond.

Cameron has projected ambivalence on the issue, saying he wants the country to remain inside Europe, but only if he can win critical changes to the E.U. charter — changes his European allies have repeatedly said they are unwilling to grant.

The question will divide not only the country but also Cameron’s government, with some of his top lieutenants likely to push for an exit.

“This will not break in any way smoothly along party lines. Part of his cabinet will campaign to leave and part of his cabinet will campaign to stay,” said Ian Kearns, director of the European Leadership Network.

But the vote could break along national lines within the U.K., with Euroskeptic English voters potentially overriding the will of the more Europe-friendly Scots.

“The E.U. referendum is going to trigger a debate over the role we play in the world, and on that, the different parts of the U.K. disagree quite profoundly,” Kearns said.

Thursday’s election underscored the vast and growing political gulf between England and Scotland. Voters in both places delivered a landslide, but in England it was for the center-right Conservatives and in Scotland it was for the left-wing Scottish National Party (SNP).

Just 15 percent of Scots voted for the Conservatives, the party that will now govern the entire U.K., Scotland included, on its own terms and without the mitigating force of a coalition.

The Tories’ plans include a doubling down on austerity policies that the SNP ran pledging to reverse but that it will have little power to stop despite winning 56 of Scotland’s 59 seats in Parliament. That will likely strengthen the SNP’s argument that Scotland is better off on its own.

“It’s absolutely perfect for them. It plays to all their narratives about the differences between England and Scotland and the wickedness of the Tories,” said Torrance, who has written biographies of the SNP’s top leaders. “They can just sit back and reap the benefits.”

With the SNP dominating politics north of the border in a way that few ever imagined, the party is likely to win convincingly in Scottish parliamentary elections slated for next year and to promise another independence referendum — but to leave the timing ambiguous.

A British exit from Europe could be just the trigger the SNP needs to call another vote, following the defeat of last year’s referendum by a 10-point margin.

Having nearly presided over the breakup of the U.K. once during his tenure, Cameron will be eager to avoid a split. He struck a conspicuously unionist tone during his comments Friday outside 10 Downing Street after getting the nod from the queen to form a new government, saying he plans to lead “one nation, one United Kingdom.”

He also promised to make the Scottish Parliament “the strongest devolved government anywhere in the world,” triggering speculation that he plans to offer the Scots full power over tax and spending decisions.

But Cameron will struggle to satisfy both the Scots and the English, whose own nationalist feelings have begun to stir. Within his party, Cameron must contend with a significant contingent that has grown weary of concessions to Scotland and is becoming more vocal in its demands for England to govern its own affairs, without outside interference — from the Scots or from Europeans.

“The back-bench, conservative, Euroskeptic members are going to look to be assertive,” said Christopher Carman, politics chair at the University of Glasgow.

Cameron himself played to English national sentiment during the campaign, continually warning English voters about the dangers of a Labor government propped up by the Scottish nationalists. The tactic may have helped him to pull out a decisive victory. But having stoked English passions could complicate his efforts to hold the union together.

“The worry is that if you do play the English against the Scots in this way, you run the risk of accentuating the kind of national divisions that the U.K. has always been able to gloss over,” said Michael Kenny, a politics professor at Queen Mary University of London. “So the argument is, you’re playing with fire here.”

That idea was at the core of the emotional valedictory address that Cameron’s former coalition partner, Nick Clegg, delivered Friday when he stood down as leader of the Liberal Democrats following a disastrous election.

Rising nationalism in both Scotland and England, Clegg warned, threatens “Britain’s place in the world and the continued existence of the United Kingdom.”

“I hope,” said a teary-eyed Clegg in a message clearly aimed at least in part at Cameron, “our leaders across the U.K. realize the disastrous consequences for our way of life and the integrity of the U.K. if they continue to appeal to grievance and fear rather than hope.”

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