with whom Mr. Justice Blackmun joins, dissenting.
The Court decides that the Illinois rule disqualifying a person from voting in the primary of one political party if he has voted in the primary of another political party during the preceding 23 months imposes an impermissible burden on Illinois voters’ exercise of their right of free political association. In so doing it distinguishes Rosario v. Rockefeller, 410 U. S. 752 (1973), decided last Term. I find Rosario more difficult to distinguish than does the Court.
*66Section 7-43 of the Illinois Election Code provides that every person eligible to register to vote is entitled to vote at primary elections; it goes on to set out a number of exceptions to that general entitlement, including both persons disqualified under the 23-month rule challenged in this case and persons disqualified because they refuse to declare a party affiliation.1 Section 7-44 re*67quires a primary voter to declare his party affiliation to the primary judges at the polling place; it further provides that, if challenged, the voter must establish his right to vote.2 Section 7-45 requires a challenged voter to supply an affidavit, in a statutorily prescribed form, to establish that he is entitled to vote under § 7-43. The affidavit states, inter alia, that the affiant has' not voted in the primary of any other political party within the forbidden 23-month period.
The Illinois system of primary elections, unlike the New York system before the Court in Rosario, does not require a voter to have enrolled as a member of a party months in advance in order to be eligible to vote in that party’s primary. Illinois provides instead for a declara*68tion of party affiliation at the primary polling place. And Illinois, not surprisingly in view of its different primary system, has chosen another way to protect its interest in preventing “raiding” than has New York. It is true, as the Court makes clear, that the Illinois rule requires a voter affiliated with one party to sit out primaries during a period of 23 months in order to effectuate a switch in affiliation to another party and qualify to vote in its primaries. In this respect Illinois’ rule imposes a greater burden on its voters’ associational freedom than does New York’s, since in New York a sufficiently prescient and diligent voter can vote in a different party’s primary every year. Of course, it cannot be said whether the Illinois appellee here underwent her change in party loyalty in time, and would have taken the necessary steps to enroll, had Illinois had New York’s rule.
On the other hand, Illinois’ rule imposes a lesser burden on its previously unaffiliated voters than does New York’s. Indeed, it imposes a lesser burden on any voter who has, for whatever reason, failed to vote in the primary of another party within the past 23 months. Such voters are not required to foresee their interest in the primary by eight or more months, as are New York voters under the rule upheld in Rosario. As a practical matter, a voter is not required to swear that he has not participated in the primary of another party as a condition of his right to vote unless he is challenged. In these respects the Illinois rule is more closely tailored to the State’s interest in preventing “raiding” than is the New York rule. Voters who have recently demonstrated loyalty to another party by voting in its primary, are more likely than those who have not to engage in “raiding.” Moreover, challenges for violations of the 23-month rule are not likely to be made where no serious danger of “raiding” is perceived.
*69Both the Illinois rule struck down today and the New York rule upheld in Rosario restrict voters’ freedom to associate with the political party of their choice. In both instances the State has sought to justify the restrictions as promoting the State’s legitimate interest in preventing “raiding.” • While neither rule is perfectly fashioned to accomplish that and no other result, I cannot conclude that the Illinois rule imposes a significantly greater burden on the exercise of associational freedom than does the New York rule we upheld last Term in Rosario.
Ill. Rev. Stat., c. 46, §7-43, provides:
“Every person having resided in this State 6 months and in the precinct 30 days next preceding any primary therein who. shall be a citizen of the United States above the age of 21 years, shall be entitled to vote at such primary.
“The following regulations shall be applicable to primaries:
“No person shall be entitled to vote at a primary:
“(a) Unless he declares his party affiliations as required by this Article;
“(b) Who shall have signed the petition for nomination of a candidate of any party with which he does not affiliate, when such candidate is to be voted for at the primary;
“(c) Who shall have signed the nominating papers of an independent candidate for any office for which office candidates for nomination are to be voted for at such primary; or
“(d) If he has voted at a primary held under this Article 7 of another political party within a period of 23 calendar months next preceding the calendar month in which such primary is held: Provided, participation by a primary elector in a primary of a political party which, under the provisions of Section 7-2 of this Article, is a political party within a city, village or incorporated town or town only and entitled hereunder to make nominations of candidates for city, village or incorporated town or town offices only, and for no other office or offices, shall not disqualify such primary elector from participating in other primaries of his party: And, provided, that no qualified voter shall be precluded from participating in the primary of any purely city, village or incorporated town or town political party under the provisions of Section 7-2 of this Article by reason of such voter having voted at the primary of another political party within a period of 23 calendar months next preceding the calendar month [in which such primary] in which he seeks to participate is held.
“(e) In cities, villages and incorporated towns having a board *67of election commissioners only voters registered as provided by Article 6 of this Act shall be entitled to vote at such primary.
“(f) No person shall be entitled to vote at a primary unless he is registered under the provisions of Article 4, 5 or 6 of this Act, when his registration is required by any of said Articles to entitle him to vote at the election with reference to which the primary is held.”
Ill. Rev. Stat., c. 46, § 7-44 provides: “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 primaiy.”