In a Jan. 23 speech, UK Prime Minister David Cameron plans to promise allowing the British people to vote on whether to stay in the European Union. The Conservative leader wants to renegotiate the UK’s relationship with the EU before asking people to vote. Once that has been done, the British people can vote either to accept it or to leave the EU, Cameron will say. Such a vote, if it were to occur, is unlikely to take place before 2017. But Cameron’s proposal comes at a challenging time for the EU, as voters question the value of the bloc amid economic weakness and chronic unemployment.