I’ve been seeing a lot of Democratic partisans defend New York’s voting restrictions, namely, the closed primary with an absurdly early deadline for changing registration. If you wanted to switch parties or switch from unaffiliated to a party, you were required to have done so by October—a time when many (probably most) people were not actively following the election.
Just as many partisans have adopted the Roberts Court’s definition of corruption (defining it down to “quid pro quo” and denying that corporate contributions constitute the “appearance of corruption”), so, too, do they seem to be siding with the conservative faction of the Court in another decision: 1973’s Rosario v. Rockefeller, the Supreme Court decision that upheld the constitutionality of New York’s restrictive voting rules.
The decision was 5-4. Justices Harry Blackmun, Warren Burger, William Rehnquist, Byron White, and Potter Stewart sided with the State of New York. Justices Lewis Powell, William Brennan, Thurgood Marshall, and William Douglas dissented.
The Segal-Cover score rates the ideology of the Supreme Court justices since 1937. Blackmun, Burger, and Rehnquist are among the top five most conservative. Brennan and Marshall are tied with several others as most liberal.
Somewhat ironically, the only liberal siding with New York (Stewart) wrote the majority opinion, and the only conservative siding against New York (Powell) wrote the dissent.
Although written by a conservative, the dissent nonetheless represents the views of the Supreme Court’s liberal faction.
What did it say about New York’s law?
The State likewise contends this is "not a disenfranchising statute." [Footnote 2/7] The Court apparently views this statute as a mere "time deadline" on petitioners' enrollment that disadvantages no identifiable class and that postpones through the next primary, rather than denies altogether, petitioners' voting and associational rights. [Footnote 2/8] I cannot agree. Deferment of a right, especially one as sensitive and essential as the exercise of the first duty of citizenship, can be tantamount to its denial. And any statute which imposes for eight or 11 months an absolute freeze on party enrollment and the consequent right to vote totally disfranchises a class of persons who, for quite legitimate reasons, decide to register closer than eight months to the primary date and those who, for equally legitimate reasons, wish to choose or alter party affiliation. Our decisions, moreover, have never required a permanent ban on the exercise of voting and associational rights before a constitutional breach is incurred. Rather, they have uniformly recognized that any serious burden or infringement on such "constitutionally protected activity" is sufficient to establish a constitutional violation, Dunn v. Blumstein, supra, at 405 U. S. 343; NAACP v. Button, 371 U. S. 415, 371 U. S. 438 (1963); Reynolds v. Sims, supra, at 377 U. S. 561-562.
(Emphasis added)
You can read the full dissent here.