The New Jersey Constitution of 1947 (Annotated) Art. V, § I, ¶ 8

8. Whenever a Governor-elect or Lieutenant Governor-elect shall have failed to qualify within six months after the beginning of the term of office, or whenever for a period of six months a Governor or Lieutenant Governor in office, or person administering the office, shall have remained continuously absent from the State, or shall have been continuously unable to discharge the duties of the office by reason of mental or physical disability, the office shall be deemed vacant. Such vacancy shall be determined by the Supreme Court upon presentment to it of a concurrent resolution declaring the ground of the vacancy, adopted by a vote of two-thirds of all the members of each house of the Legislature, and upon notice, hearing before the Court and proof of the existence of the vacancy.