There’s no denying it, skipping the debate hurt Trump in Iowa. Last night on CNN (I know, I know, it’s CNN, but they actually had pretty unbiased coverage) they mentioned how Cruz an Rubio were splitting the establishment votes and Rubio peeled votes away from Trump.
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I honestly don't think so. Iowa is not an election in the normal sense. I think Trump not going to every county in Iowa did more to hurt him there than skipping a debate.