Because we have shapefiles (GIS data files) of the Chicago precinct boundaries from Tuesday's 2015 Mayoral election we can use software to match them up against any other data set where we have shapefiles, including 2010 US census data. I ran an intersect on the precinct boundary shapefiles against the 2010 census data by census tract (and then prorated the vote totals based on the percentage of land area overlap) so that I could merge data on median household income, education as measured by the percentage of people in a census tract that had a bachelor's degree or higher and also a much more granular estimation of race than the tracker from the other night. It yielded some interesting results.
Early voting starts in a little over three weeks (March 23rd) so these two candidates have very little time to persuade voters. It will be interesting to see which of these two campaigns tries to win over new voters vs. which ones just focus in increasing turnout among the subsets of voters where they have the most support.
It probably won't come as a surprise for you to learn that the Mayor did better with affluent voters than the less affluent voters but it did surprise me to learn that a small majority (50.3%) of voters on Tuesday live in census tracts where the median household income is less than $60,000. The Mayor only won that group 41-34 as opposed to the people who live in census tracts with median household income above $60,000 where the Mayor's margin was greater at 50-33. There is a pretty clear financial divide for these two candidates that may prove beneficial for GOTV strategies.
In census tracts with a majority Hispanic population Garcia won an outright victory 56-34, however only 15% of Tuesdays voters live in those areas. On the other hand Emanuel won a clear victory in census tracts with a majority white population 53-32 and 37% of Tuesday's voters live in those areas. Even though Garcia has a natural base with Hispanic voters that base is smaller than the voting population of other ethnic groups.
34% of the voters who live in majority African American census tracts voted for one of the candidates that didn't qualify for the runoff, these voters are now coveted by both candidates. Among the voters who live in majority African American census tracts Emanuel's support is roughly the same regardless of household income. For example the AA voters who live in census tracts with a median HH income between $0 - $20,000 supported him at 42.5% while the AA voters with median HH income between $80,000 - $100,000 supported him at 41.5%. On Tuesday Emanuel won the support of more AA voters than any other candidate and whatever message it was that won him that support seemed to work the same regardless of the voter's income.
On the other hand, Garcia's support among the voters who live in majority AA census tracts did vary by income and he had greater support among the more affluent African American voters than the less affluent. For example the AA voters who live in census tracts with a median HH income between $20,000 - $40,000 supported him at 21% while the AA voters with median HH income between $100,000 - $120,000 supported him at 36%. Garcia has two challenges here 1) he earned a greater rate of support among affluent AA voters on Tuesday but the vast majority of the AA voters on Tuesday came from the less affluent census tracts (1/3 of the AA voters came from tracts with median HH income less than $40,000 and 82% less than $60,000) so he'll have to tailor his persuasive message toward the less affluent if he wants to improve his support rate, and 2) he has a difficult needle to thread in that his best GOTV strategy for the city overall is to focus on voters in < $60,000 census tracts while his best performing AA subsets are the more affluent ones.
Voters in majority white census tracts tended to be somewhat more affluent than their counterparts in majority AA or majority Hispanic census tracts. For example only 7% of voters who live in majority white census tracts had a median HH income under $60,000 whereas 82% of voters who lived in either of AA or Hispanic majority census tracts had a median HH income under $60,000. So voters in majority white census tracts tend towards the higher income brackets compared to their counterparts in AA or Hispanic majority tracts and there is a clear correlation between an increase in income bracket and an increase in support for the Mayor but there is still a ray of hope for Garcia among middle class white voters. A good majority of white voters (59%) live in census tracts with a median HH income between $60,000 - $100,000 and of all of the subsets of white voters this is where Emanuel did the worst, falling just below 50%. Also, even though Fioretti didn't win much support anywhere this was the subset of voters where he was the strongest. Garcia has the opportunity to make some inroads with middle class white voters.
When I ran the numbers I included data about education as measured by the percentage of people in each census tract that had a bachelor's degree or higher but I haven't included this data in this analysis mostly because those numbers track pretty closely to the income bracket numbers. Higher income areas tend to have a higher percentage of college educated people so the conclusions tend to mirror one another.
Election day is a little more than 5 weeks away and in a little more than 3 weeks early voters can start casting ballots again so there isn't much time to turn out voters and there is even less time to win over new ones. For either campaign to emerge successful they're going to have to study these data subsets and find their winning formula.