European leaders have a lot on their minds these days: There's the ever-growing refugee crisis, the rise of the continent's far right and the constant threat of more economic problems in the euro zone.
And then there's British Prime Minister David Cameron hopping from capital to capital, reminding them that even more trouble looms later this year in the form of an in-or-out referendum on the United Kingdom's membership in the European Union.
Some opinion polls suggest that Europe's other crises are pushing Britain toward the "out" door. So Mr. Cameron, who wants to see Britain remain in a reformed EU, spent his week flying from Berlin to Budapest, hoping to separately persuade German Chancellor Angela Merkel and Hungarian Prime Minister Viktor Orban – one the continent's most powerful politicians, the other its most unpredictable one – to make concessions that will help him convince British voters that the EU is capable of change, and thus worth staying inside.
Mr. Cameron has been on a near-constant tour of European capitals since he was re-elected last May with a mandate to hold a referendum on Britain's EU membership. His next major lobbying opportunity will come at the end of the month, when EU leaders will gather on the sidelines of the World Economic Forum in Davos.
"Support for our membership has declined over many years. So I am negotiating changes which will address the concerns of the British people," Mr. Cameron wrote in an article published on Thursday in Germany's Bild magazine.
A poll released the same day by Britain's ORB International found that 54 per cent of British voters who had made up their minds were planning to vote to leave the EU in the referendum that Mr. Cameron is expected to call in the next few months.
However, more than a fifth of respondents said they were still unsure which way they would cast their ballots.
(Telephone polls, which proved more accurate during last year's general election, give a wide lead to the pro-EU camp, while Internet polls consistently show a much tighter race.)
Many Britons are believed to be awaiting the outcome of Mr. Cameron's attempted renegotiation of Britain's deal with the EU, in order to see what kind of union they are deciding on. The ballot question has already been set – "Should the United Kingdom remain a member of the European Union or leave the European Union?" – with the only options being "leave" or "remain."
The referendum, which pundits expect to be held either in June or early in the fall, has the potential to fracture not only the European Union, but the United Kingdom itself – as well as Mr. Cameron's governing Conservative Party, which holds a slim majority of just five seats in the 650-member House of Commons.
Anand Menon, director of the UK in a Changing Europe program at King's College London, said the most pro-EU parts of the United Kingdom are London followed by Scotland, Wales and Northern Ireland. Anti-EU sentiment prevails in the rest of England beyond London.
It's a situation that could either see English votes dragging Scots, Welsh and Irish out of the EU against their will – likely setting in motion another referendum on Scottish independence, among other consequences – or an angry "little England" held in the EU against its will.
Another unanswered question is whether Mr. Cameron can hold his party together through a hard-fought referendum campaign. The Conservative Party has been bitterly divided over the question of the EU since the Margaret Thatcher years, with some MPs quitting the party to join the UK Independence Party, which is openly anti-EU.
After initially saying all ministers in his government must support the Remain camp, Mr. Cameron reversed course this week and said he would allow cabinet members to campaign for whichever side they support.
None of the EU's other 27 members wants to see the exit of Britain – a linchpin member since joining in 1973, though not a member of either the euro zone or the borderless Schengen Area. The problem is, few in Europe want to give Mr. Cameron what he wants, either.
Mr. Cameron's most contentious demand is a suspension of benefits to EU citizens who come to Britain for work, until they have been residents for at least four years. Many see the proposed change as contravening EU law, which guarantees the free movement of labour within the 28-nation bloc.
"Yes to being as open as possible to keeping Britain in the community," said Jakub Kumoch, a foreign and European policy expert on Poland's National Development Council. But no, he said, to anything that compromises the principle of free movement of labour.
"There is a widespread belief that if we agree on that, we'll open a Pandora's Box. Everyone will say: 'Yes free trade, yes freedom of movement, but here and there we want an exception.' It would damage the community."
Mr. Cameron is also seeking a reduction in red tape, new rules to protect non-euro economies within the EU's single market and an exemption for Britain from the EU's stated goal of "ever closer union," allowing national parliaments to veto new laws made in Brussels.
He will probably be able to claim at least some progress on those fronts following an EU summit next month. But both Ms. Merkel and European Commission President Jean-Claude Juncker have signalled that there will be far less flexibility on the key demand about suspending U.K. benefits for newly arrived EU citizens.
Mr. Orban suggested that Hungary was willing to make a deal on everything but Mr. Cameron's benefits demands, warning that citizens of one EU country should never be looked at as migrants or "parasites" by another EU member.
"The problem is David Cameron can't bring home the deal because the deal he wants is in contravention of EU laws," Prof. Menon said.
Mr. Cameron's decision to allow cabinet ministers to campaign for either side touched off speculation that a Conservative heavyweight such as London Mayor Boris Johnson, a minister without portfolio in Mr. Cameron's government, or Home Secretary Theresa May could seize the opportunity to lead the Leave camp and perhaps win the hearts of the Conservative Party rank-and-file, which is broadly anti-EU.
Mr. Johnson and Ms. May are viewed as two leading contenders to replace Mr. Cameron – who has said he will not seek a third term in office in 2020 – as Conservative leader. Another favourite in the undeclared race is Chancellor of the Exchequer George Osborne, a close Cameron ally who is expected to help lead the Remain camp.
Graham Brady, head of the powerful 1922 Committee of Conservative backbenchers, told The Globe and Mail that Mr. Cameron's decision to let cabinet ministers campaign according to their beliefs was "a very sensible thing to do" because it avoided putting senior politicians in a situation where they might have felt they had to resign from government over its official pro-EU position.
Mr. Brady said he was waiting to see what kind of deal Mr. Cameron could reach with European leaders, but he suggested that he was among those leaning toward joining the Leave camp.
"I have been prepared to wait until it's clear what the deal is that is offered at the end of the renegotiation," he said in a telephone interview. "But I'm not, at the moment, hopeful that we'll get a sufficient renegotiation that will satisfy my expectations."
One key to the referendum's outcome will be how Europe looks to British voters at the moment the referendum is held.
Mr. Cameron is believed to favour holding a referendum as soon as possible, perhaps in June or July, so that the Conservatives can put the EU debate behind them and refocus on other issues of government. But Mr. Brady suggested that a vote in September or October is more likely.
A later date – after another summer in which the EU is expected to receive hundreds of thousands of refugees from the Middle East, Africa and South Asia – might bolster the Leave campaign as anti-migrant sentiment blends with anti-EU feeling.
Mr. Cameron promised during last year's election campaign that he would hold an in-or-out referendum by 2017 at the latest. However, a 2017 date is considered unlikely for fear the debate could influence French and German elections scheduled for next year.
"David Cameron doesn't want to have a referendum when there are people dying on Greek beaches. He doesn't want to have one in the middle of a crisis going on in the euro zone either," Prof. Menon said. "It's a perception thing, and there is evidence to suggest that if he has it at a wrong time, it could have an impact."
But Prof. Menon said he believes that, in the end, Britain would vote to remain in the EU.
"Very few people in Britain like the EU, or actively want to be in the EU," he said. But that doesn't mean that British voters are ready to leap into the unknown of life outside the European Union, he added. "There's a plurality that's scared of the consequences if we leave."