The 1965 New Jersey Senate elections were held on November 2.
The elections were the first held after the Supreme Court's Reynolds v. Sims decision, which held that New Jersey's single-seat county apportionment was unconstitutional. The ruling forced New Jersey to grant multiple seats to its largest counties (and eventually, switch to single-member districts that did not follow county lines).
The election also coincided with a landslide re-election victory for Democratic governor Richard J. Hughes. The result was a majority for the Democratic Party, the first since 1915.
Until 1965, the New Jersey State Senate was composed of 21 senators, with each county electing one senator. 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"), New Jersey entered a decade-long period of reapportionment.
The overall effect of the reapportioning was to reduce representation for rural counties and increase representation for more populous urban counties, bringing the per person population closer to parity.
In 1965, the Senate was increased to 29 members, with larger counties given multiple seats and some smaller counties sharing one or two senators:
Districts where the difference of total votes between the top two parties was under 10%: