GOP strategy in Chicago
During the 1970s, and into the 80s, Republican strategy in Chicago was: 1) keep the base Republican vote; 2) win the White Progressive vote; 3) win the Black middle class; and, 4) win White ethnic populists.
That worked for a lot of “moderate” Republicans, including Jim Thompson, Bernard Carey, and, later on, Jim Edgar. The strategy started to unravel after the election of Mayor Harold Washington in 1983. White Progressives and Black middle class could no longer be counted on to always vote for “moderate” Republicans.