Political parties in this country traditionally have been characterized by a fluidity and overlap of philosophy and membership. And citizens generally declare or alter party affiliation for reasons quite unconnected with any premeditated intention to disrupt or frustrate the plans of a party with which they are not in sympathy. Citizens customarily choose a party and vote in its primary simply because it presents candidates and issues more responsive to their immediate concerns and aspirations. Such candidates or issues often are not apparent eight to 11 months before a primary. That a citizen should be absolutely precluded so far in advance from voting in a party primary in response to a sympathetic candidate, a new or meaningful issue, or changing party philosophies in his State, runs contrary to the fundamental rights of personal choice and expression which voting in this country was designed to serve.

Whatever state interest exists for preventing cross-overs from one party to another is appreciably lessened where, as in the case of petitioners, there has been no previous affiliation with any political party. The danger of voters in sympathy with one party "raiding" another party is insubstantial where the voter has made no prior party commitment at all. Certainly, the danger falls short of the overriding state interest needed to justify denying petitioners, so far in advance, the right to declare an initial party affiliation and vote in the party primary of their choice.

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Partisan political activities do not constantly engage the attention of large numbers of Americans, especially as party labels and loyalties tend to be less persuasive than issues and the qualities of individual candidates. The crossover in registration from one party to another is most often impelled by motives quite unrelated to a desire to raid or distort a party's primary. To the extent that deliberate raiding occurs, it is usually the result of organized effort which depends for its success upon some relatively immediate concern or interest of the voters. This type of effort is more likely to occur as a primary date draws near. If New York were to adopt a more reasonable enrollment deadline, say 30 to 60 days, the period most vulnerable to raiding activity would be protected. More importantly, a less drastic enrollment deadline than the eight or 11 months now imposed by New York would make the franchise and opportunities for legitimate party participation available to those who constitutionally have the right to exercise them.