Legislative districts were redrawn by a 10-member bi-partisan New Jersey Apportionment Commission to reflect population changes following the 1970 U.S. Census.

After the U.S. Supreme Court decision Reynolds v. Sims required legislative districts to be approximately equal in population (a principle known as "one man, one vote").

The map was changed again in 1967, and again in 1971, as the state adjusted to the one man, one vote ruling.

District 6 (now comprising Mercer and Hunterdon County) also switched from electing its senators at-large to electing them from two single-member districts because it became composed of more than one county.

The new districts were divided as follows: Two incumbent Republican senators were defeated for re-election:[3] One incumbent Republican Senator who was denied party support for another term ran in the general election as an Independent candidate and was defeated; Republicans held this seat:[4] No incumbent Democratic senators were defeated for re-election.