Donald Trump experiences his worst day in the race as some polls no longer show him as the frontrunner. Tune into World News Tonight with David Muir .\r
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Donald Trump experiences his worst day in the race as some polls no longer show him as the frontrunner. Donald Trump continues to lead Republican U.S. .\r
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Donald Trump continues to lead Republican U.S. presidential candidates among likely GOP caucusgoers in Iowa, but retired neurosurgeon Dr. Ben Carson is .\r
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