Yes, 18%.
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But it's worse than that, really:
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Recognise that evangelical Christians make up about 18% of the population.  They have essentially a 100% voter participation rate.  They vote virtually 100% for the Oil Party.  
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When you grasp the meaning of those facts, you begin to understand the true nature and magnitude of the problem.
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More-or-less, an organised (and, astonishingly, taxpayer-subsidised) religious group is destroying the democratic process in this country.
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So much for government based on reason and the rule of law ...