Whisper it quietly but there's actually a chance that a vote to leave the EU would not ultimately result in Britain leaving (i.e. if the terms negotiated were not popular, etc). The political consequences - especially within the Conservative Party - would be something else of course, Jesus.
low turnout and extremely narrow margin could make the referendum decision less stark and give rise to reason for Parliament to make it owns mind on the issue.
If that happened I can't imagine that going over well with voters