9:29 PM: The AP has now called the race for Quigley. So, why did he win?
The answer begins with name recognition: Quigley has been appearing on ballots in IL-05's environs for over a decade now, as he was first elected to the Cook County Board of Commissioners in 1998. Although most voters probably have no idea what the Board of Commissioners does, they know Quigley's name, and that's worth something in a 12-candidate field. By contrast, Feigenholtz' and Fritchey's State House districts cover just a small fraction of IL-05's territory.
The rap I heard against Feigeholtz, who had the SEIU's endorsement and a lot of money in the race, is simply that she fell somewhat flat on the stump. Not dislikable by any means, but just a little stiff, unable to engage votes in an election where they were having a great deal of difficulty engaging.
9:13 PM: Quigley now leads both John Fritchey and Sarah Feigenholtz by about 2,400 votes with 88% of precincts reporting. There probably aren't more than about 6,000-7,000 votes remaining to be counted, and those votes are being split amount literally 12 candidates, so it's next to impossible to see how he loses.
Cook County Commissioner Mike Quigley, whom we dubbed the favorite last week to succeed Rahm Emanuel, appears as though he'll be the next Congressman from Illinois' 5th Congressional District. With about 70% of the ballots in, Quigley leads John Fritchey by about 2,100 votes and Sara Feigenholtz by about 2,500 in city of Chicago precincts (.pdf), more than enough to offset his slight deficit in the suburbs.
The Republican race, for the moment, is too early to call, with Tom Hanson and Rosanna Pulido within about 100 votes of one another amidst very low turnout.