LONDON — This is a curious election for anyone who cares about Britain. If David Cameron, the Conservative prime minister, is returned to office, the country will face a referendum in 2017 that could take the United Kingdom out of the European Union and into strategic irrelevance. Two years will be lost to a paralyzing debate in which the worst of anti-European British bigotry will have free rein.

If Ed Miliband, the Labour Party leader, becomes prime minister, he will have in some form to rely on the support of the surging Scottish National Party (S.N.P.), which wants to break up Britain. Miliband vows that he will not succumb to the whims of Nicola Sturgeon, the S.N.P. leader, but this is a man whose determination to reach Downing Street has already seen the political equivalent of fratricide. His promises should be viewed in that cold light.

Pay your money and take your pick: a Britain outside Europe or a rump Britain. Of course, it’s not that simple. Cameron could prevail in his muddled attempt to keep the country in Europe while “repatriating” greater, as yet unspecified powers from Brussels. He may control the malign little-England genie he’s let out of the bottle to appease the right of his Tory party. Miliband may be able to make use of the S.N.P. without becoming its hostage. The worst is not inevitable.

Still, these unhappy choices point to an uneasy and divided Britain. Cameron has overseen an economic recovery that is the envy of continental Europe. Unemployment is at its lowest rate in several years. Jobless French and Spanish youths flock to Britain to find work. The prime minister has steadied the ship.