By Elizabeth Piper LONDON (Reuters) - Among the ranks of campaigners to keep Britain in the European Union is a small group of Prime Minister David Cameron's closest advisers. For these aides, the scale of victory is as important as victory itself. This team is targeting close to 60 percent of the "Remain" vote in a June 23 referendum that will decide whether Britain stays in the EU or leaves, members of Cameron's inner circle told Reuters in interviews. Without a clear margin, Cameron will remain vulnerable on an issue that brought down two of his predecessors, Margaret Thatcher and John Major, and has bedeviled his Conservative Party for decades.
