Much has been said, and assumed, about the role race in the primary contest between Aldermanic President Lewis Reed (who is black) and Mayor Francis Slay (who is white). Many assumptions were very safe. The mayor’s stronghold was southwest city where the 12th, 16th and 23rd wards are more than 90% white. Reed, although living in (and former alderman of) the city’s centrally located 6th Ward, was expected to receive a large majority of his votes from north city where the 1st, 4th, 21st, 22nd and 27th wards are more than 95% black.
In a city that is very nearly 50/50 white/black, the stage was potentially set for a very close and very divided vote. The starting point for the graphic below is the (admittedly very basic) mayoral primary if the vote split perfectly along racial lines. The question is then, where did each candidate exceed or fall short of this measure? When a ward is greater than 90% a single race, one would still expect a candidate of a different race to receive votes, and so any divergence isn't particularly revelatory. Here's how the final votes diverged from the racial composition of the ward.