The American people are just more complicated that that.
Persons not white NOR black, and especially Asians, are making their presence known in New Orleans and its near-in suburbs, and it now appears that nearly 5% of the vote cast today will be of such racial origin.
On the other hand, perhaps there still IS a dichotomy as before, but between black and non-black, at least according to what is seen now. Asians and persons resembling such seem to be casting upwards of 62% of their vote for Terrell, and it is possible that among persons from India especially, the Republican support approaches totality. Louisiana's Hispanic community, while not large, tends to be recently arrived and very Catholic, and the pro-abortion and non-religious tone of Landrieu and the Democrats cannot have helped there either.