Ancestry.com's home page today indicates that the Chicago [Illinois] Voter Registrations for these years:
are "new." I'm not certain what is new about these databases or the accompanying images. These records (and the index) have been on Ancestry.com for years. The images, when I looked at them today, appear to be the same ones. I did not experiment with the index enough to know if it was different or not.
The image below is part of the 1888 entry for Thomas Frame:
You can search these years of Chicago voter records on Ancestry.com:
They do include naturalization information as shown in the right hand page corresponding to the above entries:
