On May 29, Memorial Day, the Illinois House unanimously passed SB 1933. It had passed the Senate on May 5. It provides that adult citizens known by the state government to exist will automatically be registered to vote, unless they opt out. The Senate vote had also been unanimous. The bill still isn’t through the legislative process, because the Senate needs to vote on whether to approve a House amendment. That will probably happen on May 30.
Because the Illinois voter registration form doesn’t ask applicants to choose a party, Illinois does not have the problem of asking these new registrants about their choice of party.
Assuming the bill is signed into law, after a few years the effect will probably be to make it more likely that a petition signature will be considered valid. A larger proportion of signers (compared to the present day) will be registered voters.