A federal lawsuit is questioning Illinois new same-day registration rules for the general election.

The suit, brought by a north-central Illinois Republican congressional candidate and a party committee claims the change is unconstitutional because there isn’t equal access, particularly for voters in less populated and Republican-leaning areas.

Several groups object that claim though, arguing a change would cause chaos and deny people the right to vote.

Illinois tested same day registration in 2014 and made it permanent in 2015.