"Congressman Schock, your liberal record speaks for itself. You understandably would like to hide the reality that you are a pro-stimulus spending, pro-ObamaCare, pro-debt limit increase, pro-tax increase, pro-labor 'Republican,' but all the evidence points to that very fact," Chocola writes.

It's a response to what the group characterized as a "defensive reaction" to Schock's being named to the Club for Growth's new website, launched Wednesday, on which Schock and eight of his colleagues were listed as targets for a primary challenge.

The website lists lawmakers that have a lifetime Club for Growth rating of less than 70 percent but currently serve in a district that GOP presidential nominee Mitt Romney won with more than 60 percent of the vote. That makes them susceptible to a challenge from the right with little risk to the party as a whole.

Schock's office issued a release shortly after the site went live defending his record and charging that "Club for Growth’s endgame is for Congress to become even more strident and gridlocked."

"Aaron Schock however, believes he was elected to represent the people of the 18th District, not the board of directors of Club for Growth. He will not cede his responsibility to represent all the people of the 18th District to any self-anointed guardian of the economic interests of the district," the release reads.

In response, Chocola asks eight questions about Schock's record, on what he characterizes as a "pro-labor union voting record," his votes "against 40 out of 45 amendments to cut spending," and others. Many of the bills Chocola highlights passed with strong Republican support.

And in closing, Chocola accuses Schock of "pretending" in defending his record.

"Congressman Schock, please stop pretending to be a fiscal conservative. The voters of Illinois’s 18th Congressional District are not blind: they can tell when someone is pretending to be something they’re not," Chocola writes.