10 ILCS 5/7-44
Any person desiring to vote at a primary shall state his name, residence and party affiliation to the primary judges, one of whom shall thereupon announce the same in a distinct tone of voice, sufficiently loud to be heard by all persons in the polling place. When article 4, 5 or 6 is applicable the Certificate of Registered Voter therein prescribed shall be made and signed and the official poll record shall be made. If the person desiring to vote is not challenged, one of the primary judges shall give to him one, and only one, primary ballot of the political party with which he declares himself affiliated, on the back of which such primary judge shall endorse his initials in such manner that they may be seen when the primary ballot is properly folded. If the person desiring to vote is challenged he shall not receive a primary ballot from the primary judges until he shall have established his right to vote as hereinafter provided. No person who refuses to state his party affiliation shall be allowed to vote at a primary.
A person who declares his party affiliation with a statewide established political party and requests a primary ballot of such party may nonetheless also declare his affiliation with a political party established only within a political subdivision, and may also vote in the primary of such local party on the same election day, provided that such voter may not vote in both such party primaries with respect to offices of the same political subdivision. However, no person declaring his affiliation with a statewide established political party may vote in the primary of any other statewide political party on the same election day.
10 ILCS 5/7-44