I believe that you might find that the expected turnout in those counties in an off year election should be low and it will be a banner turn out year for Republicans. The Democrats might be taking one for the gipper as it were. The whole thing just sounds very strange to me.
I imagine that you're right on the low turnout.
I believe only about 170,000 votes were cast in the Democratic primary while over 400,000 votes were cast on the Republican side for SC.