I’ve wondered about that too, but never looked into it. Try this link to search:
http://www.discoverthenetworks.org/
“Making It: How Chicago shaped Obama”
by Ryan Lizza
http://www.newyorker.com/reporting/2008/07/21/080721fa_fact_lizza?currentPage=all
Toni Preckwinkle was Barak Obama’s alderman (alderwoman) in 1995 Chicago. She had to give her okay for Obama to throw his hat in the ring the first time he ran for elected office, for Illinois state congressman.