The New Jersey Constitution of 1947 (Annotated) Art. IV, § IV, ¶ 1

1. Any vacancy in the Legislature occasioned otherwise than by expiration of term shall be filled by election for the unexpired term only at the next general election occurring not less than 51 days after the occurrence of the vacancy, except that no vacancy shall be filled at the general election which immediately precedes the expiration of the term in which the vacancy occurs. For the interim period pending the election and qualification of a successor to fill the vacancy, or for the remainder of the term in the case of a vacancy occurring which cannot be filled pursuant to the terms of this paragraph at a general election, the vacancy shall be filled within 35 days by the members of the county committee of the political party of which the incumbent was the nominee from the municipalities or districts or units thereof which comprise the legislative district.