Dem super-PAC ties Chicago Republicans to Joe Walsh

All three are facing uphill battles to hold onto their Democratic-leaning seats, though Walsh has the toughest path to victory because of his hardline conservatism. That the group is using him to attack the other two, rather than going after him directly, shows how endangered he is.

"The bottom line is that as much as they’re willing to let Joe Walsh take the heat for his offensive outspokenness and extreme positions, Bob Dold and Judy Biggert are just as out of step with the middle class as Joe Walsh is," House Majority PAC Executive Director Alixandria Lapp said in a statement.

The group teamed up with the SEIU for the Walsh ad and is running another ad against Biggert that features photos of her with House Republican leadership and President George W. Bush while saying she's "trying to hide in plain sight." They plan to debut another ad against Dold next week in the expensive Chicago media market.