Cruz is too principled to do it, but my take on Trump's questioning of Cruz's faith, is to ask Trump how many Christians he knows who have never asked God for forgiveness.
Trump's statement that he has never asked God for forgiveness pretty much defines the matter for anyone who has ever read the New Testament.
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catnipman has never read the New Testament. (or likely the Old Testiment either; both require confession, and repentance)