British politician and leader of the UKIP party Nigel Farage talks to members of the media as he launches his party's campaign for Britain to leave the EU,  in London, Friday.
British politician and leader of the UKIP party Nigel Farage talks to members of the media as he launches his party's campaign for Britain to leave the EU, in London, Friday. Credit: AP Photo

LONDON — British voters will decide in one month whether or not to deal a historic hammer blow to European integration by putting their island nation on an independent path outside the European Union.

The choice on June 23 is simple: In or Out. But the ramifications of a vote to leave are complex and uncertain.

The campaign has hardly been a model of cool, reasoned argument. “Leave” campaigner and former London Mayor Boris Johnson has compared the EU’s goals to those of Adolf Hitler, while “Stay“-supporting Prime Minister David Cameron has suggested that a decision to leave the 28-nation bloc would please Islamic State extremists.

EU advocates argue that leaving the bloc would batter Britain’s economy, costing each household thousands, while the “Leave” side says Britain has blithely forfeited the independence it once fought so fiercely to defend — and can reclaim it only by walking away from the EU and its byzantine rules.

British security chiefs have weighed in (most want to stay) along with business leaders (stay, for the most part) and 300 well-known figures from the arts (stay, stay, stay). World leaders have chimed in, including President Barack Obama (stay) and Canadian Prime Minister Justin Trudeau, who argues Britain would be foolhardy to turn its back on its EU trading partners.

The prospect of a British exit — a Brexit — hangs over the future of the EU.