Nation

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The final six GOP candidates sparred in Saturday's ninth Republican presidential debate, taking on topics, including foreign policy, the Islamic State, 9/11 and replacing Justice Scalia. Jon Greenberg of Politifact joins William Brangham to fact check what they said.

The pileup, which involved 50 or more vehicles, including roughly a dozen tractor-trailers, happened around 9:30 Saturday morning, and it was likely caused in part by the extreme winter weather that has hit much of the northeastern United States.