I'm not sure I want Emanuel defeated.  He's pissed me off (Duckworth, for instance), but I think we need to wait until November to see if he's the master strategist some think he is.  Perhaps the same thing goes for Schumer.

However, there is a candidate who could beat Emanuel in the primary.  His name is Tom Tunney and he's an openly gay Chicago alderman and business owner.
He is immensely popular and well known far beyond his ward.