http://www.chicagoreader.com/obama_reader/what_makes_obama_run/
This other one, a retrospective, testifies to Obama's tactical prowess in avoiding a frontal clash with Daley's political machine without succumbing to its seduction:
http://www.chicagoreader.com/obama_reader/rising_star/
These two other pieces are also informative, one an interview with Axelro, the other on Rahm Emanuel's self-reinvention to get elected representative:
http://www.chicagoreader.com/obama_reader/david_axelrod/
http://www.chicagoreader.com/obama_reader/rahm_emanuel/
The issue has other stories, but I haven't read them yet.