David Belcher says Eric Cantor 's polling was off , but likely others were off , too . Belcher : Change in opinion and opinion helped to change conventional wisdom . Cantor probably never really had the big lead he thought he had , says Cornell .
Cornell Belcher says Eric Cantor 's polling was off , but likely voters were off , too . Belcher : Shifts in demographics and polarization helped to dislodge conventional wisdom . Cantor probably never really had the big lead he thought he had , says Belcher .