Democrats just don't win Senate races in North Carolina during Presidential years—and most of those "wins" have come with GOP candidates a lot more polarizing than Liddy Dole.
Has any Republican senator polled below a challenger in NC, or within 5 points, in an election year before? How were Helms-Gantt polling at this time in '96?
Historical patterns hold up until they don't, and it takes strong confidence to write off a poll showing the incumbent behind a challenger by one point several months before Election Day.
Also, I think the Obama effect on African-American turnout, so easily and wrongly hyped in other examples, is a genuine asset to Hagen when the white vote is not as polarized as it is elsewhere.