There also is often a spike in checks after a dramatic incident of gun violence.

CNN: Gun checks top two million for fourth-straight month

Opponents promise a political fight, with an NRA spokesman saying Tuesday that the group has experienced what he called an "unprecedented" spike in membership numbers since new calls for gun control began in the past month.

CNN: Pushback on Obama's plan to stem gun violence

The matter has led to intense hours-long hearings at the State Capitol, where lawmakers and anti-violence advocates from Chicago which has seen a spike in violence have been pitted against gun rights advocates from less populated and more conservative areas.

NPR: Ill. Gov. Wants Appeal Of Concealed Carry Ruling