Nothing will close it completely but I think there needs to be a harder Brexit deal on the ballot. Something like Johnson's that doesn't break the GFA but satisfies the three general beneficial ideas (as they see it) that Brexit was sold on: sovereignty from the ECJ, immigration controls on EU migrants and the UK becoming an independent trading nation. If remain wins Farage's et al's claim that 'it wasn't a real Brexit' would carry little weight because if they can't sell a hard Brexit to the British public then how could they sell the hardest Brexit? In a soft Brexit vs Remain ballot all you would hear is 'betrayal', 'Brexit has been stolen' 'duped' and so on. If a soft Brexit goes through all you would hear is 'we're still controlled by the EU' 'betrayal', 'Brexit has been stolen' 'duped' and so on. The whole debate would still be completely live and the bitterness amplified. Even having the three options on the ballot could work although I'm opposed to a soft Brexit because it's a completely ridiculous deal to accept.