- Security is still one of four main topics of the fractious debate because it's not been won, writes Nic Robertson
- David Cameron raised the specter of UK exit potentially leading to a Europe-wide war
- With the vote teetering on a knife edge, the security debate could be crucial
(CNN)UK citizens are poised to vote on a crucial decision about whether to stay or leave the European Union (EU) -- but the debate has been stalked by the fear that one big terror attack in the UK before Thursday's poll could influence the outcome.
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