New Jersey Statutes Title 19. Elections 19 § 62-7

a. the county clerk shall mail the ballot of a political party to each voter in the municipality who is registered as being affiliated with the political party as of the 21st day before the day of the primary election; and

b. a voter who is not affiliated with any political party who wishes to vote in the primary of a political party shall apply to the county clerk or municipal clerk in writing for the ballot of the political party in whose primary the voter wishes to vote, or designate a political party affiliation for the first time by whatever means permitted by law, and the application or designation shall be presented to the clerk through the day of the election.