With national polls showing President Barack Obama and Republican presidential nominee Mitt Romney running neck-and-neck heading into Election Day, a narrow margin in the popular vote outcome seems well within the realm of possibility. As HuffPost's Mark Blumenthal points out, most of the major national sample polls show either an exact tie, or give a nominal advantage to Obama.
But the 2012 presidential election certainly wouldn't be the first U.S. election to be decided by a small margin. We've compiled a list of some of the closest races in history.
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