N.J. Stat. § 40:20-35.11b
In the case of a vacancy occurring with respect to a member of the board of chosen freeholders who was elected as the candidate of a political party which at the last preceding general election held received the largest number of votes or the next largest number of votes in the county for members of the board of chosen freeholders, for the interim period pending the election and qualification of a permanent successor to fill the vacancy, or for the interim period constituting the remainder of the term in the case of a vacancy occurring which cannot be filled pursuant to section 2 of this act at a general election, the vacancy shall be filled within 35 days by a member of the political party of which the person who vacated the office was the candidate at the time of his election thereto. The interim successor shall be selected by the appropriate political party's county committee in the same manner prescribed in subsections a. and b. of R.S. 19:13-20 for selecting candidates to fill vacancies among candidates nominated at primary elections, and a statement of the selection of that successor shall be certified to and filed with the county clerk in the same manner prescribed by subsection d. of that section for certifying statements concerning the selection of such candidates.
N.J.S. § 40:20-35.11b