An estimated 30% or more of the soldiers and officers in the confederate forces were from "slave-holding families." Which, even if we are to take your unsourced claim as accurate, still leaves the other 70%, or a clear majority. To put that figure in perspective, if Bush were to win the election by 55% it would be called a landslide.
I hope Bush wins by a "landslide," but that traditionally is at the 60% level. The 1972 election is correctly called a "popular vote landslide." "Electoral College" landslides are less well-defined, because the Electoral College has a tendency to create the appearance of a mandate when one might not actually exist, as in the case of both of Clinton's elections.
If Bush does win real big, >15%, he has a good chance of getting a filibuster-proof Senate too.