In Kusper v. Pontikes, the U.S. Supreme Court ruled in favor of a Chicago voter who challenged an Illinois law that prohibited individuals from voting in a party's primary if they had voted in another party's primary within the preceding 23 months. The plaintiff, Georgia Pontikes, argued that this restriction violated her First Amendment rights to freedom of association and speech by limiting her ability to express political preferences through voting. The court agreed with Pontikes' argument, stating that while states have legitimate interests in maintaining stable political systems and preventing "party raiding" (where voters temporarily switch parties to influence primaries), these interests did not justify such severe restrictions on voters' constitutional rights. Therefore, the court declared Illinois’ restrictive law unconstitutional.

In the dissenting opinion for Kusper v. Pontikes, Justice Rehnquist argued that the majority's decision was inconsistent with previous rulings and overly broad in its interpretation of First Amendment rights. He contended that Illinois' 23-month restriction on party-switching did not infringe upon voters' freedom of association because it only applied to primary elections, which he viewed as a part of internal party affairs rather than public electoral processes. Furthermore, he believed this rule served legitimate state interests by preventing "party raiding" (where members from one political group temporarily join another to manipulate their candidate selection) and maintaining stable political parties. Therefore, according to him, such restrictions were constitutional as they aimed at preserving the integrity of the electoral process without significantly burdening individual voting rights.