U.K. Prime Minister David Cameron has reached a deal with Europe's other leaders on new terms for Britain's membership in the European Union, and says the promised referendum on whether to remain in the EU will take place on June 23. He has four months to persuade a closely divided country to stay.

For the sake of the U.K. and the EU both, he needs to succeed -- but he's leading a divided government and a divided Conservative Party. This isn't going to be easy.  

Michael Gove, the justice minister, and five other cabinet members have said they'll campaign for exit. Many Tory members of Parliament -- even, by some accounts, a majority -- agree with them. Boris Johnson, the popular mayor of London and a contender to replace Cameron as prime minister, has said he'll join the leave campaign.

Cameron is a strong campaigner, as he proved in the most recent general election, and he'll need to be. He can hardly claim that remaining in the EU is self-evidently in Britain's interests: Throughout, he's said the choice would depend on whether Europe could be reformed. Although the deal he's done is valuable (contrary to the claims of Britain's fervidly anti-EU news media), the new terms aren't as far-reaching as the prime minister had hoped.

The agreement exempts Britain from the EU treaty commitment to "ever closer union"; it recognizes the separate status of EU members that aren't part of the euro single-currency area; it keeps regulation of the U.K.'s financial sector with the Bank of England; and it meets Cameron halfway on EU migrants' access to U.K. welfare benefits.

Those are real gains, even if they don't create the looser "live and let live" EU that Cameron has called for. At least for now, a more flexible EU isn't what most of the union's governments want.

They're wrong about that: There's every sign voters in other countries don't want closer political integration and would welcome more of the flexibility Cameron has proposed. But the main thing for U.K. voters isn't that Europe failed to seize this chance to rethink its future. It's that Cameron has secured Britain's special standing as a country with its own currency and a variety of so-called opt-outs from EU initiatives.

In a way, the U.K. therefore gets the best of both worlds: the main benefits of EU membership (unrestricted access to Europe's single market) without its greatest costs (euro-induced stagnation).

Over the next few months, a lot will be heard from euroskeptics about the freedoms that the EU takes away and the obligations it imposes. It's true that EU membership involves a loss of formal sovereignty, something that Britons (no less than Americans) are sensitive to. Yet a medium-sized country deeply embedded in Europe's larger economy would be deluding itself to think separation from the EU would widen its real choices or help it prosper.  

A vote to leave would be too much of a gamble. "I believe we are stronger, safer and better off inside this reformed European Union," Cameron says. He's right.

David Fuller's view

The UK’s vote in June, to either leave or stay in the EU, may be close but I think David Cameron’s gains described above, following a very energetic and diplomatic campaign, should be enough to ensure that the UK remains within the EU.  If so, I do not think that the deciding factor will be fear, caused by the Prime Minister’s warning that a vote in favour of Brexit would be a “leap in the dark”.  Instead, I think most voters will conclude that Britain’s international role will be more influential if it remains within the EU.