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He could however think that even a 10% risk of total fucking disaster is not worth taking firmly on the chin (because it would be him alone who takes it, if they arrange something devious to facilitate no-deal) - if it means effigies of him and his immediates will be burned on bonfires for decades to come.
If however parliament sleep walks in to tacitly agreeing to no-deal, then yah, they'll take it, because they won't take the rap for disaster alone.
You need to bear in mind that someone like Raab is not in the same frame of reference as we are- he won’t think that it will destroy the party, he thinks it will be a success. He is, by some measures, insane.