Weighing the results from each of Chicago’s 2,069 precincts as ranked-choice votes would offer a better approximation — and FairVote says it is embarking this week on that daunting task. But even using the much larger data set will not account for the way an actual ranked-choice system, now in use in roughly 20 jurisdictions nationwide, changes the texture of campaigns, making them less negative as candidates angle to be second and even third choices.