N.J. Stat. § 40:41A-35.1
In the case of a vacancy occurring with respect to a county executive 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 35 of P.L. 1972, c.154 (C.40:41A-35) 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 the candidate's 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. Members of the political party's county committee who are empowered to select a candidate for the vacated office shall only nominate a candidate from the floor during the selection meeting called under R.S. 19:13-20 by the chairman or chairmen of the committee and shall present written evidence of the nominee's acceptance of the nomination. 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.
The county clerk shall thereupon issue to the interim successor a certificate of selection based upon that filed statement of selection, and shall sign the clerk's name and affix the seal of the State thereto, and shall without delay deliver that statement to the person so selected.
N.J.S. § 40:41A-35.1